JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank

done Radioactivity Total Questions - 176

• question_answer1)
  Radioactive substance do not emit    [CPMT 1997; AIEEE 2003]
  A)
             Electron                                  done clear
  B)
             Helium nucleus done clear
  C)
             Positron                                  done clear
  D)
             Proton done clear
  View Solution play_arrow

• question_answer2)
  In a radioactive substance at \[t=0\], the number of atoms is \[8\times {{10}^{4}}\]. Its half life period is 3 years. The number of atoms \[1\times {{10}^{4}}\] will remain after interval [MP PMT/PET 1988]
  A)
             9 years                                     done clear
  B)
             8 years done clear
  C)
             6 years                                     done clear
  D)
             24 years done clear
  View Solution play_arrow

• question_answer3)
  The half-life period of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years is [NCERT 1980; SCRA 1994; JIPMER 1997 CBSE PMT 1994; MNR 1998; MP PMT 2004; DPMT 2004]
  A)
             \[\frac{1}{4}\]                       done clear
  B)
             \[\frac{1}{2}\] done clear
  C)
             \[\frac{1}{8}\]                       done clear
  D)
             \[\frac{1}{16}\] done clear
  View Solution play_arrow

• question_answer4)
  During a negative beta decay                     [IIT 1987; MNR 1990]
  A)
             An atomic electron is ejected done clear
  B)
             An electron which is already present within the nucleus is ejected done clear
  C)
             A neutron in the nucleus decays emitting an electron done clear
  D)
             A part of the binding energy is converted into electron done clear
  View Solution play_arrow

• question_answer5)
  Some radioactive nucleus may emit                           [IIT 1986]
  A)
             Only one \[-13.6\ eV\] or \[\gamma \]at a time done clear
  B)
             All the three \[_{92}{{U}^{238}}\] and \[\gamma \] one after another done clear
  C)
             All the three \[\alpha ,\ \beta \] and \[\gamma \] simultaneously done clear
  D)
             Only\[\alpha \] and \[\beta \] simultaneously done clear
  View Solution play_arrow

• question_answer6)
  Which can pass through 20 cm thickness of the steel [MNR 1985; CPMT 1990; RPET 2000]
  A)
             \[\alpha -\]particles           done clear
  B)
             \[\beta -\]particles done clear
  C)
             \[\gamma -\]rays                done clear
  D)
             Ultraviolet rays done clear
  View Solution play_arrow

• question_answer7)
  The half-life period of radium is 1600 years. Its average life time will be                                  [MP PET/PMT 1988]
  A)
             3200 years                              done clear
  B)
             4800 years done clear
  C)
             2319 years                              done clear
  D)
             4217 years done clear
  View Solution play_arrow

• question_answer8)
  What percentage of original radioactive atoms is left after five half lives                [AFMC 1996; RPMT 1996]
  A)
             0.3%                                         done clear
  B)
             1% done clear
  C)
             31%                                           done clear
  D)
             3.125% done clear
  View Solution play_arrow

• question_answer9)
  Beta rays emitted by a radioactive material are  [IIT 1983; ISM Dhanbad 1994; AFMC 1997; BHU 2000; AIEEE 2002]
  A)
             Electromagnetic radiation done clear
  B)
             The electrons orbiting around the nucleus done clear
  C)
             Charged particles emitted by nucleus done clear
  D)
             Neutral particles done clear
  View Solution play_arrow

• question_answer10)
  Alpha rays emitted from a radioactive substance are [CBSE PMT 1999; RPET 2000]
  A)
             Negatively charged particles done clear
  B)
             Ionised hydrogen nuclei done clear
  C)
             Doubly ionised helium atom done clear
  D)
             Uncharged particles having the mass equal to proton done clear
  View Solution play_arrow

• question_answer11)
  In the given reaction\[_{z}{{X}^{A}}{{\to }_{z+1}}{{Y}^{A}}{{\to }_{z-1}}{{K}^{A-4}}{{\to }_{z-1}}{{K}^{A-4}}\]Radioactive radiations are emitted in the sequence   [AIIMS 1982; CBSE PMT 1993; AFMC 1999; MP PET 2002]
  A)
             \[\frac{2{{\varepsilon }_{0}}hc}{{{e}^{2}}}\]               done clear
  B)
             \[\beta ,\ \alpha ,\ \gamma \] done clear
  C)
             \[\gamma ,\ \alpha ,\ \beta \]                                          done clear
  D)
             \[\beta ,\ \gamma ,\ \alpha \] done clear
  View Solution play_arrow

• question_answer12)
  Half-life of \[B{{i}^{210}}\] is 5 days. If we start with 50,000          atoms of this isotope, the number of atoms left over after 10            days is [MP PET 1993]
  A)
             5,000                                        done clear
  B)
             25,000                                      done clear
  C)
             12,500                                      done clear
  D)
             20,000 done clear
  View Solution play_arrow

• question_answer13)
  A nucleus of atomic mass A and atomic number Z emits \[{{M}_{1}}\]particles. The atomic mass and atomic number of the resulting nucleus are                                                   [CPMT 1982]
  A)
             A, Z                                           done clear
  B)
             A + 1, Z done clear
  C)
             A, Z + 1                                    done clear
  D)
             \[A-4,\ Z-2\] done clear
  View Solution play_arrow

• question_answer14)
  The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 seconds. Its half-life is [CPMT 1990, 97]
  A)
             2 seconds                               done clear
  B)
             4 seconds done clear
  C)
             5 seconds                               done clear
  D)
             6 seconds done clear
  View Solution play_arrow

• question_answer15)
  Radioactivity was discovered by
  A)
             Becquerel                              done clear
  B)
             Pierre Curie done clear
  C)
             Roentgen                               done clear
  D)
             Rutherford done clear
  View Solution play_arrow

• question_answer16)
  The decay constant \[\lambda \] of the radioactive sample is the probability of decay of an atom in unit time, then [CBSE PMT 1990]
  A)
             \[\lambda \] decreases as atoms become older done clear
  B)
             \[\lambda \] increases as the age of atoms increases done clear
  C)
             \[\lambda \] is independent of the age done clear
  D)
             Behaviour of \[\lambda \] with time depends on the nature of the activity done clear
  View Solution play_arrow

• question_answer17)
  The average life T  and the decay constant \[\lambda \] of a radioactive nucleus are related as                   [CPMT 1983]
  A)
             \[T\lambda =1\]                  done clear
  B)
             \[T=\frac{0.693}{\lambda }\] done clear
  C)
             \[\frac{T}{\lambda }=1\]  done clear
  D)
             \[{{\lambda }_{1}},\ {{\lambda }_{2}},\ {{\lambda }_{3}}\] done clear
  View Solution play_arrow

• question_answer18)
  If T is the half-life of a radioactive material, then the fraction that would remain after a time \[\frac{T}{2}\] is      [MP PMT 1992]
  A)
             \[\frac{1}{2}\]                       done clear
  B)
             \[\frac{3}{4}\] done clear
  C)
             \[\frac{1}{\sqrt{2}}\]         done clear
  D)
             \[\frac{\sqrt{2}-1}{\sqrt{2}}\] done clear
  View Solution play_arrow

• question_answer19)
  If the decay or disintegration constant of a radioactive substance is\[\beta \], then its half life and mean life are respectively [IIT 1989; MNR 1990; MP PET 1995, 97, 99,  2002; MP PMT 1999, 2002; UPSEAT 2002]
  A)
             \[\begin{matrix}    1  \\    \lambda   \\ \end{matrix}\] and \[\frac{{{\log }_{e}}2}{\lambda }\]      done clear
  B)
             \[\frac{{{\log }_{e}}2}{\lambda }\]and \[\begin{matrix}    1  \\    \lambda   \\ \end{matrix}\] done clear
  C)
             \[\lambda \ {{\log }_{e}}2\]and\[\begin{matrix}    1  \\    \lambda   \\ \end{matrix}\]                                done clear
  D)
             \[\begin{matrix}    \lambda   \\    {{\log }_{e}}2  \\ \end{matrix}\] and \[\begin{matrix}    1  \\    \lambda   \\ \end{matrix}\] (loge 2 can be written as ln 2) done clear
  View Solution play_arrow

• question_answer20)
  Which of the following is in the increasing order for penetrating power                                  [IIT 1994; RPET 2003]
  A)
             \[\alpha ,\ \beta ,\ \gamma \]                                          done clear
  B)
             \[\beta ,\ \alpha ,\ \gamma \] done clear
  C)
             \[\gamma ,\ \alpha ,\ \beta \]                                          done clear
  D)
             \[\gamma ,\ \beta ,\ \alpha \] done clear
  View Solution play_arrow

• question_answer21)
  The half-life of a radioactive element which has only \[\frac{1}{32}\] of its original mass left after a lapse of 60 days is [MP PET 1992; DPMT 2002]
  A)
             12 days                                    done clear
  B)
             32 days done clear
  C)
             60 days                                    done clear
  D)
             64 days done clear
  View Solution play_arrow

• question_answer22)
  The half-life of \[B{{i}^{210}}\]is 5 days. What time is taken by (7/8)th part of the sample to decay             [MNR 1986; Pb. PMT 2001]
  A)
             3.4 days                                   done clear
  B)
             10 days done clear
  C)
             15 days                                    done clear
  D)
             20 days done clear
  View Solution play_arrow

• question_answer23)
  A radioactive nucleus undergoes a series of decay according to the scheme            \[A\xrightarrow{\alpha }{{A}_{1}}\xrightarrow{\beta }{{A}_{2}}\xrightarrow{\alpha }{{A}_{3}}\xrightarrow{\gamma }{{A}_{4}}\]            If the mass number and atomic number of A are 180 and 72 respectively, then what are these number for A4 [Roorkee 1986; MP PET 2002; KCET 2003; DPMT 2005]
  A)
             172 and 69                              done clear
  B)
             174 and 70 done clear
  C)
             176 and 69                              done clear
  D)
             176 and 70 done clear
  View Solution play_arrow

• question_answer24)
  Radioactivity is
  A)
             Irreversible process           done clear
  B)
             Self disintegration process done clear
  C)
             Spontaneous process       done clear
  D)
             All of the above done clear
  View Solution play_arrow

• question_answer25)
  Half-life of radioactive element depends upon [NCERT 1978; AFMC 1996]
  A)
             Amount of element present done clear
  B)
             Temperature done clear
  C)
             Pressure done clear
  D)
             Nature of element done clear
  View Solution play_arrow

• question_answer26)
  The decay constant of radium is \[4.28\times {{10}^{-4}}\]per year. Its half life will be                                      [MNR 1990]
  A)
             2000 years                              done clear
  B)
             1240 years done clear
  C)
             63 years                                  done clear
  D)
             1620 years done clear
  View Solution play_arrow

• question_answer27)
  Which of the following is not a mode of radioactive decay [NCERT 1978]
  A)
             Positron emission               done clear
  B)
             Electron capture done clear
  C)
             Fusion                                      done clear
  D)
             Alpha decay done clear
  View Solution play_arrow

• question_answer28)
  Atomic mass number of an element thorium is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of alpha and beta particles emitted is                                [CPMT 1985; Pb. PET 2003]
  A)
             \[\alpha =3,\ \beta =3\]   done clear
  B)
             \[\alpha =6,\ \beta =4\] done clear
  C)
             \[\alpha =6,\ \beta =0\]   done clear
  D)
             \[\alpha =4,\ \beta =6\] done clear
  View Solution play_arrow

• question_answer29)
  A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is  [NCERT 1984; MNR 1995; MP PMT 1995]
  A)
             Less than 1 mg                     done clear
  B)
             \[\frac{1}{4}gm\] done clear
  C)
             \[\frac{1}{2}gm\]                done clear
  D)
             1 gm done clear
  View Solution play_arrow

• question_answer30)
  A radio-isotope has a half- life of 5 years. The fraction of the atoms of this material that would decay in 15 years will be [NCERT 1984; MP PMT 1996; MP PET 1997]
  A)
             1/8 done clear
  B)
             2/3 done clear
  C)
             7/8 done clear
  D)
             5/8 done clear
  View Solution play_arrow

• question_answer31)
  Curie is a unit of
  A)
             Length                                     done clear
  B)
             It is not any unit done clear
  C)
             Activity                                    done clear
  D)
             Atomic number done clear
  View Solution play_arrow

• question_answer32)
  Three \[\alpha -\]particles and one \[\beta -\]particle decaying takes place in series from an isotope \[_{88}R{{a}^{238}}\]. Finally the isotope obtained will be                                                          [CPMT 1989; DCE 2000]
  A)
             \[_{84}{{X}^{220}}\]           done clear
  B)
             \[_{86}{{X}^{222}}\] done clear
  C)
             \[_{83}{{X}^{224}}\]           done clear
  D)
             \[_{83}{{X}^{215}}\] done clear
  View Solution play_arrow

• question_answer33)
  Half-life of a radioactive substance is T.  The time taken for all the nuclei to disintegrate will be
  A)
             2T   done clear
  B)
             T2 done clear
  C)
             4T   done clear
  D)
             Uncertain done clear
  View Solution play_arrow

• question_answer34)
  The half-life of polonium is 140 days. After how many days, 16 gm polonium will be reduced to 1 gm  (or 15g will decay)                                                      [CPMT 1997; Pb. PET 2002; BHU 2004]
  A)
             700 days                                 done clear
  B)
             280 days                                 done clear
  C)
             560 days                                 done clear
  D)
             420 days done clear
  View Solution play_arrow

• question_answer35)
  An archaeologist analyses the wood in a prehistoric structure and finds that \[{{C}^{14}}\](Half-life = 5700 years) to \[{{C}^{12}}\]is only one- fourth of that found in the cells buried plants. The age of the wood is about                                       [NCERT 1982]
  A)
             5700 years                              done clear
  B)
             2850 years done clear
  C)
             11,400 years                          done clear
  D)
             22,800 years done clear
  View Solution play_arrow

• question_answer36)
  The correct order of ionizing capacity of \[a,\ \beta \]and \[\gamma -\]rays is     [CBSE PMT 2000]
  A)
             \[\alpha >\gamma >\beta \]  done clear
  B)
             \[\alpha >\beta >\gamma \] done clear
  C)
             \[\alpha <\beta <\gamma \]  done clear
  D)
             \[\alpha >\beta >\gamma \] done clear
  View Solution play_arrow

• question_answer37)
  A radioactive element emits 200 particles per second. After three hours 25 particles per second are emitted. The half-life period of element will be
  A)
             50 minutes                             done clear
  B)
             60 minutes done clear
  C)
             70 minutes                             done clear
  D)
             80 minutes done clear
  View Solution play_arrow

• question_answer38)
  The decay constant of a radioactive element is 0.01 per second. Its half-life period is  [DPMT 2001]
  A)
             693 sec                                     done clear
  B)
             6.93 sec done clear
  C)
             0.693 sec                                 done clear
  D)
             69.3 sec done clear
  View Solution play_arrow

• question_answer39)
  Consider a radioactive material of half-life 1.0 minute. If one of the nuclei decays now, the next one will decay [MNR 1994]
  A)
             After 1 minute done clear
  B)
             After \[\frac{1}{{{\log }_{e}}2}\] minute done clear
  C)
             After \[\frac{1}{N}\]minute, where N is the number of nuclei present at that moment done clear
  D)
             After any time done clear
  View Solution play_arrow

• question_answer40)
  The half-life of the isotope \[_{11}N{{a}^{24}}\]is 15 hrs. How much time does it take for \[\frac{7}{8}th\] of a sample of this isotope to decay [MP PET 1994]
  A)
             75 hrs                                       done clear
  B)
             65 hrs done clear
  C)
             55 hrs                                       done clear
  D)
             45 hrs done clear
  View Solution play_arrow

• question_answer41)
  If the half-life of a radioactive sample is 10 hours, its mean life is                                               [MP PET 1994]
  A)
             14.4 hours                              done clear
  B)
             7.2 hours done clear
  C)
             20 hours                                  done clear
  D)
             6.93 hours done clear
  View Solution play_arrow

• question_answer42)
  If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in  4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm               [MP PMT 1994]
  A)
             In 8 minutes                          done clear
  B)
             In 12 minutes done clear
  C)
             In 16 minutes                        done clear
  D)
             In 20 minutes done clear
  View Solution play_arrow

• question_answer43)
  16 gm sample of a radioactive element is taken from Bombay to Delhi in 2 hour and it was found that 1 gm of the element remained (undisintegrated). Half life of the element is                                  [MP PMT 1994]
  A)
             2 hour                                      done clear
  B)
             1 hour done clear
  C)
             \[\frac{1}{2}hour\]             done clear
  D)
             \[\frac{1}{4}hour\] done clear
  View Solution play_arrow

• question_answer44)
  Unit of radioactivity is Rutherford. Its value is  [MP PMT 1994]
  A)
             \[3.7\times {{10}^{10}}\]disi tegrations/sec done clear
  B)
             \[3.7\times {{10}^{6}}\]disintegrations/sec done clear
  C)
             \[1.0\times {{10}^{10}}\] disintegrations/sec done clear
  D)
             \[1.0\times {{10}^{6}}\] disintegrations/sec done clear
  View Solution play_arrow

• question_answer45)
  In which radioactive disintegration, neutron dissociates into proton and electron                                              [AFMC 1995]
  A)
             \[H{{e}^{++}}\] emission done clear
  B)
             \[\beta -\]emission done clear
  C)
             \[\gamma -\]emission      done clear
  D)
             Positron emission done clear
  View Solution play_arrow

• question_answer46)
  The count rate of a Geiger- Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to 5\[{{s}^{-1}}\]after 2 hours. The initial count rate was [CBSE PMT 1995]
  A)
             25\[{{s}^{-1}}\]                    done clear
  B)
             80\[{{s}^{-1}}\] done clear
  C)
             625\[{{s}^{-1}}\]                  done clear
  D)
             20\[{{s}^{-1}}\] done clear
  View Solution play_arrow

• question_answer47)
  What is the respective number of \[\alpha \]and \[\beta \] particles emitted in the following radioactive decay            \[_{90}{{X}^{200}}{{\to }_{80}}{{Y}^{168}}\] [CBSE PMT 1995; Pb. PMT 2004]
  A)
             6 and 8                                     done clear
  B)
             8 and 8 done clear
  C)
             6 and 6                                     done clear
  D)
             8 and 6 done clear
  View Solution play_arrow

• question_answer48)
  A radioactive reaction is\[_{92}{{U}^{238}}{{\to }_{82}}P{{b}^{206}}\]. How many \[\alpha \]and \[\beta \]particles are emitted [BHU 1995; CET 1998; RPET 1996; BHU 2000; AMU (Engg.) 2000]
  A)
             \[10\alpha ,\ 6\beta \]      done clear
  B)
             4 protons, 8 neutrons done clear
  C)
             6 electrons, 8 protons       done clear
  D)
             \[6\beta ,\ 8\alpha \] done clear
  View Solution play_arrow

• question_answer49)
  A radioactive substance has a half-life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be  [BHU 1995; 2000]
  A)
             12.5%                                       done clear
  B)
             87.5% done clear
  C)
             8.5%                                         done clear
  D)
             25.1% done clear
  View Solution play_arrow

• question_answer50)
  A element used for radioactive carbon dating for more than 5600 years is                                             [BHU 1995]
  A)
             \[C-14\]                                   done clear
  B)
             \[U-234\] done clear
  C)
             \[U-238\]                                done clear
  D)
             \[Po-94\] done clear
  View Solution play_arrow

• question_answer51)
  After two hours, one- sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half-life of the isotope is  [Bihar MEE 1995; Manipal MEE 1995; EAMCET 1994 MP PMT 1997; DPMT 2002; AFMC 2000, 05]
  A)
             15 minutes                             done clear
  B)
             30 minutes done clear
  C)
             45 minutes                             done clear
  D)
             1 hour done clear
  View Solution play_arrow

• question_answer52)
  N atoms of a radioactive element emit n alpha particles per second. The half life of the element is [MP PET 1995; MP PMT 1997, 2003]
  A)
             \[\frac{n}{N}\]sec               done clear
  B)
             \[\frac{N}{n}\] sec done clear
  C)
             \[\frac{0.693\ N}{n}\] sec        done clear
  D)
             \[5,099\ c{{m}^{-1}}\] sec done clear
  View Solution play_arrow

• question_answer53)
  A radioactive nucleus \[_{92}{{X}^{235}}\]decays to \[_{91}{{Y}^{231}}\]. Which of the following particles are emitted                       [MP PMT 1995]
  A)
             One alpha and one electron  done clear
  B)
             Two deuterons and one positron done clear
  C)
             One alpha and one proton done clear
  D)
             One proton and four neutrons done clear
  View Solution play_arrow

• question_answer54)
  The radioactive nucleus \[_{7}{{N}^{13}}\]decays to \[_{6}{{C}^{13}}\] through the emission of                                                 [MP PET 1996]
  A)
             Neutron                                  done clear
  B)
             Proton                                     done clear
  C)
             Electron                                  done clear
  D)
             Positron done clear
  View Solution play_arrow

• question_answer55)
  The counting rate observed from a radioactive source at t=0 second was 1600 counts per second and at t=8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t=6 seconds, will be [MP PET 1996; UPSEAT 2000;  Pb. PET 2004; Kerala PET 2005]
  A)
             400 done clear
  B)
             300 done clear
  C)
             200 done clear
  D)
             150 done clear
  View Solution play_arrow

• question_answer56)
  The radioactive decay of uranium into thorium is expressed by the equation\[_{92}^{238}U\to _{90}^{234}Th+X,\]where \['X'\]is [MP PMT 1996, 2002; AMU (Engg.) 2000]
  A)
             An electron                           done clear
  B)
             A proton                                 done clear
  C)
             A deuteron                            done clear
  D)
             An alpha particle done clear
  View Solution play_arrow

• question_answer57)
  The relationship between \[\lambda \]and half life \[({{T}_{1/2}})\]of a radioactive substance is                [RPMT 1996; MP PMT 1996]
  A)
             \[\lambda =\frac{{{\log }_{10}}2}{{{T}_{1/2}}}\]        done clear
  B)
    \[\lambda =\frac{{{\log }_{e}}2}{{{T}_{1/2}}}\] done clear
  C)
             \[\lambda =\frac{{{\log }_{2}}10}{{{T}_{1/2}}}\]        done clear
  D)
    \[\lambda =\frac{{{\log }_{2}}e}{{{T}_{1/2}}}\] done clear
  View Solution play_arrow

• question_answer58)
  In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process                                                 [MP PET 1997]
  A)
             Proton                                     done clear
  B)
             Neutron done clear
  C)
             Electron                                  done clear
  D)
             Photon done clear
  View Solution play_arrow

• question_answer59)
  The rate of disintegration of fixed quantity of a radioactive element can be increased by               [MP PMT 1997, 2003]
  A)
             Increasing the temperature done clear
  B)
             Increasing the pressure done clear
  C)
             Chemical reaction done clear
  D)
             It is not possible done clear
  View Solution play_arrow

• question_answer60)
  The half-life (T) and the disintegration constant \[(\lambda )\]of a radioactive substance are related as [MP PMT/PET 1998]
  A)
             \[\lambda T=1\]                  done clear
  B)
             \[\lambda T=0.693\] done clear
  C)
    \[\frac{T}{\lambda }=0.693\]   done clear
  D)
             \[\frac{\lambda }{T}=0.693\] done clear
  View Solution play_arrow

• question_answer61)
  The half-life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be [MP PMT/PET 1998]
  A)
             93.75%                                     done clear
  B)
             75% done clear
  C)
             25%                                           done clear
  D)
             6.25% done clear
  View Solution play_arrow

• question_answer62)
   Radon (Ra) decays into Polonium (\[{{P}_{0}}\]) by emitting an \[\alpha -\]particle with half-life of 4 days. A sample contains \[6.4\times {{10}^{10}}\]atoms of\[Rn\]. After 12 days, the number of atoms of \[{{R}_{n}}\]left in the sample will be [MP PET 1999, Pb. PMT 2004]
  A)
             \[3.2\times {{10}^{10}}\] done clear
  B)
             \[0.53\times {{10}^{10}}\] done clear
  C)
             \[2.1\times {{10}^{10}}\] done clear
  D)
             \[0.8\times {{10}^{10}}\] done clear
  View Solution play_arrow

• question_answer63)
  Decay constant of radium is\[\lambda \]. By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be [MP PET 1999; JIPMER 2001, 02]
  A)
             \[\lambda \]                          done clear
  B)
             More than \[\lambda \] done clear
  C)
             Less than \[\lambda \]      done clear
  D)
             Zero done clear
  View Solution play_arrow

• question_answer64)
  In the uranium radioactive series, the initial nucleus is \[_{92}{{U}^{238}}\]and the final nucleus is \[_{82}P{{b}^{206}}\]. When the uranium nucleus decays to lead, the number of \[\alpha -\]particles emitted will be                                   [MP PMT 1999]
  A)
             1     done clear
  B)
             2 done clear
  C)
             4     done clear
  D)
             8 done clear
  View Solution play_arrow

• question_answer65)
  After \[1\alpha \]and \[2\beta \]emissions                                                          [CBSE PMT 1999]
  A)
             Mass number reduces by 3 done clear
  B)
             Mass number reduces by 4 done clear
  C)
             Mass number reduces by 6 done clear
  D)
             Atomic number remains unchanged done clear
  View Solution play_arrow

• question_answer66)
  Which of the following is a correct statement  [IIT 1999; DPMT 2000; UPSEAT 2003]
  A)
             Beta rays are same as cathode rays done clear
  B)
             Gamma rays are high energy neutrons done clear
  C)
             Alpha particles are singly ionized helium atoms done clear
  D)
             Protons and neutrons have exactly the same mass done clear
  View Solution play_arrow

• question_answer67)
   \[^{22}Ne\]nucleus after absorbing energy decays into two \[\alpha -\]particles and an unknown nucleus. The unknown nucleus is                                                        [IIT 1999; UPSEAT 2002]
  A)
             Nitrogen                                 done clear
  B)
             Carbon done clear
  C)
             Boron                                       done clear
  D)
             Oxygen done clear
  View Solution play_arrow

• question_answer68)
  Half lives of two radioactive substances A and B are respectively 20 minutes and 40 minutes. Initially the sample of A and B have equal number of nuclei. After 80 minutes, the ratio of remaining number of A and B nuclei is [CBSE PMT 1998; JIPMER 2000]
  A)
             1 : 16                                         done clear
  B)
             4 : 1 done clear
  C)
             1 : 4                                           done clear
  D)
             1 : 1 done clear
  View Solution play_arrow

• question_answer69)
  A nucleus \[_{n}{{X}^{m}}\]emits one \[\alpha \] and one \[\beta \] particles. The resulting nucleus is [CBSE PMT 1998; BHU 2001; AFMC 2002]
  A)
             \[_{n}{{X}^{m-4}}\]            done clear
  B)
             \[_{n-2}{{Y}^{m-4}}\] done clear
  C)
             \[_{n-4}{{Z}^{m-4}}\]        done clear
  D)
             \[_{n-1}{{Z}^{m-4}}\] done clear
  View Solution play_arrow

• question_answer70)
  If the radioactive decay constant of radium is \[1.07\times {{10}^{-4}}\]per year, then its half life period is approximately equal to [AIIMS 1998]
  A)
             8,900 years                            done clear
  B)
             7,000 years done clear
  C)
             6,476 years                            done clear
  D)
             2,520 years done clear
  View Solution play_arrow

• question_answer71)
  The half-life of \[^{131}I\]is 8 days. Given a sample of \[^{131}I\]at time t = 0, we can assert that                                              [IIT 1998]
  A)
             No nucleus will decay before t = 4 days done clear
  B)
             No nucleus will decay before t = 8 days done clear
  C)
             All nuclei will decay before t = 16 days done clear
  D)
             A given nucleus may decay at any time after t = 0 done clear
  View Solution play_arrow

• question_answer72)
  Carbon \[-14\]decays with half-life of about 5,800 years. In a sample of bone, the ratio of carbon \[-14\]to carbon \[-12\]is found to be \[\frac{1}{4}\] of what it is in free air. This bone may belong to a period about x centuries ago, where x is nearest to [KCET 1994]
  A)
             \[2\times 58\] done clear
  B)
             58 done clear
  C)
             58/2                                          done clear
  D)
             \[3\times 58\] done clear
  View Solution play_arrow

• question_answer73)
  Age of a tree is determined using radio-isotope of [EAMCET (Engg.) 1995]
  A)
             Carbon                                    done clear
  B)
             Cobalt done clear
  C)
             Iodine                                      done clear
  D)
             Phosphorus done clear
  View Solution play_arrow

• question_answer74)
  An atom of mass number 15 and atomic number 7 captures an \[\alpha -\]particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be                                                              [SCRA 1994]
  A)
             14 and 2                                  done clear
  B)
             15 and 3 done clear
  C)
             16 and 4                                  done clear
  D)
             18 and 8 done clear
  View Solution play_arrow

• question_answer75)
  Which of the following statements are true regarding radioactivity (I)       All radioactive elements decay exponentially with time (II)     Half life time of a radioactive element is time required for one half of the radioactive atoms to disintegrate (III)    Age of earth can be determined with the help of radioactive dating (IV) Half life time of a radioactive element is 50% of its average life period Select correct answer using the codes given below Codes:                                                        [SCRA 1994]
  A)
             I and II                                     done clear
  B)
             I, III and IV done clear
  C)
             I, II and III done clear
  D)
             II and III done clear
  View Solution play_arrow

• question_answer76)
  In the disintegration series\[_{92}^{238}U\xrightarrow{\alpha }X\xrightarrow{\beta -}_{Z}^{A}Y\]the values of Z and A respectively will be                               [MP PMT 2003]
  A)
             92, 236                                     done clear
  B)
             88, 230 done clear
  C)
             90, 234                                     done clear
  D)
             91, 234 done clear
  View Solution play_arrow

• question_answer77)
  The particles emitted by radioactive decay are deflected by magnetic field. The particles will be [RPET 1997]
  A)
             Protons and \[\alpha -\]particles done clear
  B)
             Electrons, protons and \[\alpha -\]particles done clear
  C)
             Electrons, protons and neutrons done clear
  D)
             Electrons and \[\alpha -\]particles done clear
  View Solution play_arrow

• question_answer78)
  Half-life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be [RPET 1997]
  A)
             100 days                                  done clear
  B)
             50 days done clear
  C)
             33 days                                    done clear
  D)
             16 days done clear
  View Solution play_arrow

• question_answer79)
  In the given nuclear reaction A, B, C, D, E represents \[_{92}{{U}^{238}}{{\xrightarrow{\alpha }}_{B}}T{{h}^{A}}{{\xrightarrow{\beta }}_{D}}P{{a}^{C}}{{\xrightarrow{E}}_{92}}{{U}^{234}}\] [RPET 1997]
  A)
             A = 234, B = 90, C = 234, D = 91, E = \[\beta \] done clear
  B)
             A = 234, B = 90, C = 238, D = 94, E = \[\alpha \] done clear
  C)
             A = 238, B = 93, C = 234, D = 91, E = \[\beta \] done clear
  D)
             A = 234, B = 90, C = 234, D = 93, E = \[\alpha \] done clear
  View Solution play_arrow

• question_answer80)
  If half-life of a radioactive element is 3 hours, after 9 hours its activity becomes                 [RPMT 1997; RPET 1999]
  A)
             1/9 done clear
  B)
             1/27 done clear
  C)
             1/6 done clear
  D)
             1/8 done clear
  View Solution play_arrow

• question_answer81)
  The nucleus \[_{48}^{115}Cd\] after two successive \[{{\beta }^{-}}\] decays will give                     [CBSE PMT 1992; JIPMER 2000]
  A)
             \[_{46}^{115}Pa\]               done clear
  B)
             \[_{49}^{114}In\] done clear
  C)
             \[_{50}^{113}Sn\]               done clear
  D)
             \[_{50}^{115}Sn\] done clear
  View Solution play_arrow

• question_answer82)
  A radioactive sample with a half-life of 1 month has the label: ?Activity=2 micro curies on 1.8.1991.'' What will be its activity two months later                                                    [CBSE PMT 1992]
  A)
             1.0 micro curies                    done clear
  B)
             0.5 micro curies done clear
  C)
             4 micro curies                        done clear
  D)
             8 micro curies done clear
  View Solution play_arrow

• question_answer83)
  An element A decays into element C by a two-step process : \[A\to B+{{\ }_{2}}H{{e}^{4}}\]\[B\to C+\ 2{{e}^{-}}\] Then  [CBSE PMT 1994; AMU 2002; KCET 2003]
  A)
             A and C are isotopes          done clear
  B)
             A and C are isobars done clear
  C)
             A and B are isotopes          done clear
  D)
             A and B are isobars done clear
  View Solution play_arrow

• question_answer84)
  At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances                                      [RPMT 1996]
  A)
             1 : 1                                           done clear
  B)
             2 : 1 done clear
  C)
             1 : 2                                           done clear
  D)
             1 : 4 done clear
  View Solution play_arrow

• question_answer85)
  Which of the following isotopes is used for the treatment of cancer                                        [RPET 1996]
  A)
             \[{{K}^{40}}\]                        done clear
  B)
             \[C{{o}^{60}}\] done clear
  C)
             \[S{{r}^{90}}\]                      done clear
  D)
             \[{{I}^{131}}\] done clear
  View Solution play_arrow

• question_answer86)
  If half-life of a radioactive atom is 2.3 days, then its decay constant would be      [AFMC 1997; JIPMER 2000]
  A)
             0.1  done clear
  B)
             0.2 done clear
  C)
             0.3  done clear
  D)
             2.3 done clear
  View Solution play_arrow

• question_answer87)
  A radioactive element \[_{90}{{X}^{238}}\]decay into\[_{83}{{Y}^{222}}\]. The number of \[\beta -\]particles emitted are  [BHU 1997; JIPMER 2001, 02]
  A)
             4     done clear
  B)
             6 done clear
  C)
             2     done clear
  D)
             1 done clear
  View Solution play_arrow

• question_answer88)
  A radio isotope has a half life of 75 years. The fraction of the atoms of this material that would decay in 150 years will be                   [BHU 1997]
  A)
             66.6%                                       done clear
  B)
             85.5% done clear
  C)
             62.5%                                       done clear
  D)
             75% done clear
  View Solution play_arrow

• question_answer89)
  The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately [CBSE PMT 1997]
  A)
             0.230 per minute                 done clear
  B)
             0.461 per minute done clear
  C)
             0.691 per minute                 done clear
  D)
             0.922 per minute done clear
  View Solution play_arrow

• question_answer90)
  An artificial radioactive decay series begins with unstable \[_{94}^{241}Pu\]. The stable nuclide obtained after eight \[\alpha -\]decays and five \[\beta -\]decays is                                                 [SCRA 1998]
  A)
             \[_{83}^{209}Bi\]                done clear
  B)
             \[_{82}^{209}Pb\] done clear
  C)
             \[_{82}^{205}Ti\]                 done clear
  D)
             \[_{82}^{201}Hg\] done clear
  View Solution play_arrow

• question_answer91)
  Consider the following two statements A.       Energy spectrum of a-particles emitted in radioactive decay is discrete B.       Energy spectrum of b-particles emitted in radioactive decay is continuous                                                 [AMU (Med.) 1999]
  A)
             Only A is correct done clear
  B)
             Only B is correct done clear
  C)
             A is correct but B is wrong done clear
  D)
             Both A and B are correct done clear
  View Solution play_arrow

• question_answer92)
  The activity of a sample is 64 × 10?5 Ci. Its half-life is 3 days. The activity will become 5 × 10?6 Ci after          [MP PET 2003]
  A)
             12 days                                    done clear
  B)
             7 days done clear
  C)
             18 days                                    done clear
  D)
             21 days done clear
  View Solution play_arrow

• question_answer93)
  The half-life of radon is 3.8 days. Three forth of a radon sample decay in
  A)
             5.02 days                                done clear
  B)
             15.2 days done clear
  C)
             7.6 days                                  done clear
  D)
             11.4 days done clear
  View Solution play_arrow

• question_answer94)
  A nucleus of an element \[_{84}{{X}^{202}}\]emits an a-particle first, a b-particle next and then a gamma photon. The final nucleus formed has an atomic number                                                  [JIPMER 1999]
  A)
             200                                            done clear
  B)
             199 done clear
  C)
             83   done clear
  D)
             198 done clear
  View Solution play_arrow

• question_answer95)
  3.8 days is the half-life period of a sample. After how many days, the sample will become 1/8th of the original substance                                                                                                 [DCE 1999]
  A)
             11.4                                           done clear
  B)
             3.8 done clear
  C)
             3     done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer96)
  Plutonium decays with a half-life of 24000 years. If the plutonium is stored for 72000 years, then the fraction of plutonium that remains is                                         [CPMT 1999; MH CET 2003]
  A)
             \[\frac{1}{2}\]                       done clear
  B)
             \[\frac{1}{3}\] done clear
  C)
             \[\frac{1}{4}\]                       done clear
  D)
             \[\frac{1}{8}\] done clear
  View Solution play_arrow

• question_answer97)
  A radioactive substance emits                                [CPMT 1999]
  A)
             a-rays                                      done clear
  B)
             b-rays done clear
  C)
             g-rays                                       done clear
  D)
             All of these done clear
  View Solution play_arrow

• question_answer98)
  The large scale destruction, that would be caused due to the use of nuclear weapons is called [AFMC 1999]
  A)
             Nuclear holocaust done clear
  B)
             Thermo-nuclear reaction done clear
  C)
             Nuetron reproduction factor done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer99)
  An atomic nucleus \[_{90}T{{h}^{232}}\] emits several a and b radiations and finally reduces to \[_{82}P{{b}^{208}}\]. It must have emitted [MP PET 2003]                                              
  A)
             4a and 2b                               done clear
  B)
             6a and 4b done clear
  C)
             8a and 24b                            done clear
  D)
             4a and 16b done clear
  View Solution play_arrow

• question_answer100)
  In beta decay                                       [UPSEAT 2000; MP PMT 2000]
  A)
             The parent and daughter nuclei have same number of protons done clear
  B)
             The daughter nucleus has one proton less than the parent nucleus done clear
  C)
             The daughter nucleus has one proton more than the parent nucleus done clear
  D)
             The daughter nucleus has one neutron more than the parent nucleus done clear
  View Solution play_arrow

• question_answer101)
  A radioactive substance has a half-life of 1 year. The fraction of this material, that would remain after 5 years will be  [CPMT 2000]
  A)
             \[\frac{1}{32}\]                    done clear
  B)
             \[\frac{1}{5}\] done clear
  C)
             \[\frac{1}{2}\]                       done clear
  D)
             \[\frac{4}{5}\] done clear
  View Solution play_arrow

• question_answer102)
  The activity of a radioactive sample                         [BHU 2000]
  A)
             Can be increased by heating it done clear
  B)
             Is independent of physical parameter done clear
  C)
             Cannot be increased by any method done clear
  D)
             Both (b) and (c) done clear
  View Solution play_arrow

• question_answer103)
  A radioactive sample has half-life of 5 years. Probability of decay in 10 years will be                          [RPET 2000]
  A)
             100%                                        done clear
  B)
             75% done clear
  C)
             50%                                           done clear
  D)
             25% done clear
  View Solution play_arrow

• question_answer104)
  If half-life of a substance is 3.8 days and its quantity is 10.38 gm. Then substance quantity remaining left after 19 days will be                                                         [RPMT 2000; AFMC 2002]
  A)
             0.151 gm                                 done clear
  B)
             0.32 gm done clear
  C)
             1.51 gm                                   done clear
  D)
             0.16 gm done clear
  View Solution play_arrow

• question_answer105)
  After five half lives what will be the fraction of initial substance                                 [RPMT 2000]
  A)
             \[{{\left( \frac{1}{2} \right)}^{10}}\]                               done clear
  B)
             \[{{\left( \frac{1}{2} \right)}^{5}}\] done clear
  C)
             \[{{\left( \frac{1}{2} \right)}^{4}}\]                                  done clear
  D)
             \[{{\left( \frac{1}{2} \right)}^{3}}\] done clear
  View Solution play_arrow

• question_answer106)
  Which is the correct expression for half-life  [CBSE PMT 2000]
  A)
             \[{{(t)}_{1/2}}=\log 2\]     done clear
  B)
             \[{{(t)}_{1/2}}=\frac{\lambda }{\log 2}\] done clear
  C)
             \[{{(t)}_{1/2}}=\frac{\lambda }{\log \,\text{2}}(2.303)\]      done clear
  D)
             \[{{(t)}_{1/2}}=\frac{2.303\text{ log 2}}{\lambda }\] done clear
  View Solution play_arrow

• question_answer107)
  A nucleus \[_{Z}^{A}X\] emits an a-particle. The resultant nucleus emits a \[{{\beta }^{+}}\]particle. The respective atomic and mass no. of the final nucleus will be                                                                [MP PET 2000]
  A)
             Z ? 3, A ? 4                             done clear
  B)
             Z ? 1, A ? 4 done clear
  C)
             Z ? 2, A ? 4                             done clear
  D)
             Z, A ? 2 done clear
  View Solution play_arrow

• question_answer108)
  What fraction of a radioactive material will get disintegrated in a period of two half-lives                               [MP PET 2000]
  A)
             Whole                                      done clear
  B)
             Half done clear
  C)
             One-fourth                            done clear
  D)
             Three-fourth done clear
  View Solution play_arrow

• question_answer109)
  The activity of a radioactive sample is 1.6 curie and its half-life is 2.5 days. Its activity after 10 days will be               [MP PMT 2000]
  A)
             0.8 curie                                  done clear
  B)
             0.4 curie done clear
  C)
             0.1 curie                                  done clear
  D)
             0.16 curie done clear
  View Solution play_arrow

• question_answer110)
  In a mean life of a radioactive sample        [MP PMT 2000, 03]
  A)
             About 1/3 of substance disintegrates done clear
  B)
             About 2/3 of the substance disintegrates done clear
  C)
             About 90% of the substance disintegrates done clear
  D)
             Almost all the substance disintegrates done clear
  View Solution play_arrow

• question_answer111)
  Three fourth of the active decays in a radioactive sample in 3/4 sec. The half life of the sample is [KCET (Engg.) 2001]
  A)
             \[\frac{1}{2}\] sec               done clear
  B)
             1 sec done clear
  C)
             \[\frac{3}{8}\] sec               done clear
  D)
             \[\frac{3}{4}\] sec done clear
  View Solution play_arrow

• question_answer112)
  During mean life of a radioactive element, the fraction that disintegrates is                                          [CPMT 2001]
  A)
             e     done clear
  B)
             \[\frac{1}{e}\] done clear
  C)
             \[\frac{e-1}{e}\]                  done clear
  D)
             \[\frac{e}{e-1}\] done clear
  View Solution play_arrow

• question_answer113)
  1 Curie is equal to                                                            [BHU 2001]
  A)
             \[3\times {{10}^{10}}\] disintegrations/sec done clear
  B)
             \[3.7\times {{10}^{7}}\] disintegrations/sec done clear
  C)
             \[5\times {{10}^{7}}\] disintegrations/sec done clear
  D)
             \[3.7\times {{10}^{10}}\] disintegrations/sec done clear
  View Solution play_arrow

• question_answer114)
  In the given nuclear reaction, how many a and b particles are emitted \[_{92}{{X}^{235}}\to {{\ }_{82}}{{Y}^{207}}\]                           [AFMC 2001]
  A)
             3a particles and 2b particle done clear
  B)
             4a particles and 3b particle done clear
  C)
             6a particles and 4b particle done clear
  D)
             7a particles and 4b particle done clear
  View Solution play_arrow

• question_answer115)
  The electron emitted in beta radiation originates from  [IIT JEE (Screening) 2001]
  A)
             Inner orbits of atoms done clear
  B)
             Free electrons existing in nuclei done clear
  C)
             Decay of a neutron in a nucleus done clear
  D)
             Photon escaping from the nucleus done clear
  View Solution play_arrow

• question_answer116)
  When a radioactive substance emits an a-particle, its position in the periodic table is lowered by [AIIMS 2001]
  A)
             One place                               done clear
  B)
             Two places done clear
  C)
             Three places                         done clear
  D)
             Four places done clear
  View Solution play_arrow

• question_answer117)
  During negative b-decay                                              [RPET 2001]
  A)
             Neutron converts into proton done clear
  B)
             Proton converts into neutron done clear
  C)
             Neutron proton ratio increases done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer118)
  Half-life is measured by                                               [RPET 2001]
  A)
             Geiger-Muller counter done clear
  B)
             Carbon dating done clear
  C)
             Spectroscopic method done clear
  D)
             Wilson-Cloud chamber done clear
  View Solution play_arrow

• question_answer119)
  A radioactive nucleus emits a beta particle. The parent and daughter nuclei are                                 [EAMCET (Engg.) 2001]
  A)
             Isotopes                                 done clear
  B)
             Isotones done clear
  C)
             Isomers                                   done clear
  D)
             Isobars done clear
  View Solution play_arrow

• question_answer120)
  If a radioactive substance reduces to \[\frac{1}{16}\] of its original mass in 40 days, what is its half-life    [DCE 2001; AIIMS 2003]
  A)
             10 days                                    done clear
  B)
             20 days done clear
  C)
             40 days                                    done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer121)
  In which of the following decay, the element does not change                   [MH CET (Med.) 2001]
  A)
             b-decay                                   done clear
  B)
             a-decay done clear
  C)
             g-decay                                   done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer122)
  A radioactive nucleus with Z protons and N neutrons emits an a-particle, 2b-particles and 2 gamma rays. The number of protons and neutrons in the nucleus left after the decay respectively, are                            [AMU (Engg.) 2001]
  A)
             Z ? 3, N ? 1                             done clear
  B)
             Z ? 2, N ? 2 done clear
  C)
             Z ? 1, N ? 3                             done clear
  D)
             Z, N ? 4 done clear
  View Solution play_arrow

• question_answer123)
  99% of a radioactive element will decay between  [AMU (Engg.) 2001]                           
  A)
             6 and 7 half lives                  done clear
  B)
             7 and 8 half lives done clear
  C)
             8 and 9 half lives                  done clear
  D)
             9 half lives done clear
  View Solution play_arrow

• question_answer124)
  1 mg gold undergoes decay with 2.7 days half-life period, amount left after 8.1 days is [UPSEAT 2001]
  A)
             0.91 mg                                   done clear
  B)
             0.25 mg done clear
  C)
             0.5 mg                                     done clear
  D)
             0.125 mg done clear
  View Solution play_arrow

• question_answer125)
  Certain radio-active substance reduces to 25% of its value in 16 days. Its half-life is                                           [MP PMT 2001]
  A)
             32 days                                    done clear
  B)
             8 days done clear
  C)
             64 days                                    done clear
  D)
             28 days done clear
  View Solution play_arrow

• question_answer126)
  In the disintegration series        \[_{92}^{238}U\xrightarrow{\alpha }x\xrightarrow{\beta }_{Z}^{A}y\] The value of Z and A respectively will be [MP PET 2001; MP PMT 2001]
  A)
             92, 236                                     done clear
  B)
             88, 230 done clear
  C)
             90, 234                                     done clear
  D)
             91, 234 done clear
  View Solution play_arrow

• question_answer127)
  The decay constant of a radioactive element is \[1.5\times {{10}^{-9}}\] per second. Its mean life in seconds will be         [MP PET 2001]
  A)
             \[1.5\times {{10}^{9}}\]    done clear
  B)
             \[4.62\times {{10}^{8}}\] done clear
  C)
             \[6.67\times {{10}^{8}}\] done clear
  D)
             \[10.35\times {{10}^{8}}\] done clear
  View Solution play_arrow

• question_answer128)
  The half-life of a radioactive substance against a-decay is \[1.2\times {{10}^{7}}s\]. What is the decay rate for \[4\times {{10}^{15}}\] atoms of the substance                                                                      [AMU (Med.) 2002]
  A)
             \[4.6\times {{10}^{12}}atoms/s\]                                    done clear
  B)
             \[2.3\times {{10}^{11}}atoms/s\] done clear
  C)
             \[4.6\times {{10}^{10}}atoms/s\]                                    done clear
  D)
             \[2.3\times {{10}^{8}}\] done clear
  View Solution play_arrow

• question_answer129)
   10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is [Pb. PMT 2002]
  A)
             12.5 g                                       done clear
  B)
             10.5 g done clear
  C)
             6.03 g                                       done clear
  D)
             4.03 g done clear
  View Solution play_arrow

• question_answer130)
  In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life                                                                                               [KCET 2002]
  A)
             69.3%                                       done clear
  B)
             63% done clear
  C)
             50%                                           done clear
  D)
             37% done clear
  View Solution play_arrow

• question_answer131)
  The S.I. unit of radioactivity is           [KCET 2002]
  A)
             Roentgen                               done clear
  B)
             Rutherford done clear
  C)
             Curie                                        done clear
  D)
             Becqueral done clear
  View Solution play_arrow

• question_answer132)
  A radioactive material has an initial amount 16 gm. After 120 days it reduces to 1 gm, then the half-life of radioactive material is                                                                         [CPMT 2003]
  A)
             60 days                                    done clear
  B)
             30 days done clear
  C)
             40 days                                    done clear
  D)
             240 days done clear
  View Solution play_arrow

• question_answer133)
  Half-life of a substance is 10 years. In what time, it becomes \[\frac{1}{4}\]th part of the initial amount                  [AIEEE 2002]
  A)
             5 years                                     done clear
  B)
             10 years done clear
  C)
             20 years                                  done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer134)
  If \[{{N}_{0}}\] is the original mass of the substance of half life period \[{{T}_{1/2}}=5\] years, then the amount of substance left after 15 years is                                                                   [AIEEE 2002]
  A)
             \[{{N}_{0}}/8\]                     done clear
  B)
             \[{{N}_{0}}/16\] done clear
  C)
             \[{{N}_{0}}/2\]                     done clear
  D)
             \[{{N}_{0}}/4\] done clear
  View Solution play_arrow

• question_answer135)
  The equation \[_{z}{{X}^{A}}\,\to {{\,}_{z+1}}{{Y}^{A}}{{+}_{-1}}{{e}^{0}}+\bar{v}\] is     [CPMT 2002]
  A)
             b-emission                             done clear
  B)
             a-emission done clear
  C)
             e? capture                               done clear
  D)
             Fission done clear
  View Solution play_arrow

• question_answer136)
  The ratio activity of an element becomes 1/64th of its original value in 60 sec. Then the half life period is [MP PMT 2002]                                            
  A)
             5 sec                                         done clear
  B)
             10 sec done clear
  C)
             20 sec                                       done clear
  D)
             30 sec done clear
  View Solution play_arrow

• question_answer137)
  A radioactive substance emits                              [MP PET 2002]                             
  A)
             Electromagnetic radiation done clear
  B)
             Electrons revolving around the nucleus done clear
  C)
             Charged particles done clear
  D)
             Neutral particles done clear
  View Solution play_arrow

• question_answer138)
  If \[_{92}{{U}^{238}}\] undergoes successively 8 a-decays and 6 b-decays, then resulting nucleus is        [CBSE PMT 2002]
  A)
             \[_{82}{{U}^{206}}\]          done clear
  B)
             \[_{82}P{{b}^{206}}\] done clear
  C)
             \[_{82}{{U}^{210}}\]          done clear
  D)
             \[_{82}{{U}^{214}}\] done clear
  View Solution play_arrow

• question_answer139)
  The activity of a sample of a radioactive material is A, at time \[{{t}_{1}}\] and \[{{A}_{2}}\] at time \[{{t}_{2}}\] \[({{t}_{2}}>{{t}_{1}}).\] If  its mean life T, then                                                                  [BHU 2002]
  A)
             \[{{A}_{1}}{{t}_{1}}={{A}_{2}}{{t}_{2}}\]                       done clear
  B)
             \[{{A}_{1}}-{{A}_{2}}={{t}_{2}}-{{t}_{1}}\] done clear
  C)
             \[{{A}_{2}}={{A}_{1}}{{e}^{({{t}_{1}}-{{t}_{2}})/T}}\]             done clear
  D)
             \[{{A}_{2}}={{A}_{1}}{{e}^{({{t}_{1}}/{{t}_{2}})T}}\] done clear
  View Solution play_arrow

• question_answer140)
  Nucleus produced due to a-decay of the nucleus \[_{Z}{{X}^{A}}\] is [MP PET 2002]
  A)
             \[_{Z+2}{{Y}^{A+4}}\]       done clear
  B)
             \[_{Z}{{Y}^{A}}\] done clear
  C)
             \[_{Z-2}{{Y}^{A-4}}\]         done clear
  D)
             \[_{Z-4}{{Y}^{A-2}}\] done clear
  View Solution play_arrow

• question_answer141)
  When \[_{90}T{{h}^{228}}\] transforms to \[_{83}B{{i}^{212}}\], then the number of the emitted a- and b-particles is, respectively [MP PET 2002]
  A)
             \[8\,\alpha ,\,7\beta \]     done clear
  B)
             \[4\,\alpha ,\,7\beta \] done clear
  C)
             \[4\,\alpha ,\,4\beta \]     done clear
  D)
             \[4\,\alpha ,\,1\beta \] done clear
  View Solution play_arrow

• question_answer142)
  Which of the following processes represents a gamma-decay                                     [IIT-JEE (Screening) 2002]
  A)
             \[^{A}{{X}_{Z}}+\gamma \,\to {{\,}^{A}}{{X}_{Z-1}}+a+b\] done clear
  B)
             \[^{A}{{X}_{Z}}{{+}^{1}}{{n}_{0}}\,\to {{\,}^{A-3}}{{X}_{Z-2}}+c\] done clear
  C)
             \[^{A}{{X}_{Z}}\,\to {{\,}^{A}}{{X}_{Z}}+f\] done clear
  D)
             \[^{A}{{X}_{Z}}+{{e}_{-1}}\,\to {{\,}^{A}}{{X}_{Z-1}}+g\] done clear
  View Solution play_arrow

• question_answer143)
  The half-life of \[^{215}At\] is \[100\mu s\]. The time taken for the radioactivity of a sample of \[^{215}At\] to decay to 1/16th of its initial value is                        [IIT-JEE (Screening) 2002]
  A)
             \[400\,\mu s\]                      done clear
  B)
             \[6.3\,\mu s\] done clear
  C)
             \[40\,\mu s\]                        done clear
  D)
             \[300\mu s\] done clear
  View Solution play_arrow

• question_answer144)
  The half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its \[\frac{1}{16}\]th part [BCECE 2003]
  A)
             12 h                                           done clear
  B)
             16 h done clear
  C)
             48 h                                           done clear
  D)
             192 h done clear
  View Solution play_arrow

• question_answer145)
  A radioactive substance has an average life of 5 hours. In a time of 5 hours                                           [Orissa JEE 2003]
  A)
             Half of the active nuclei decay done clear
  B)
             Less than half of the active nuclei decay done clear
  C)
             More than half of the active nuclei decay done clear
  D)
             All active nuclei decay done clear
  View Solution play_arrow

• question_answer146)
  Which of the following rays are not electromagnetic wave [CBSE PMT 2003]
  A)
             g-rays                                       done clear
  B)
             b-rays done clear
  C)
             Heat rays                                done clear
  D)
             X-rays done clear
  View Solution play_arrow

• question_answer147)
  A sample of radioactive element has a mass of 10 gm at an instant t = 0.The approximate mass of this element in the sample after two mean lives is                          [CBSE PMT 2003]
  A)
             2.50 gm                                   done clear
  B)
             3.70 gm done clear
  C)
             6.30 gm                                   done clear
  D)
             1.35 gm done clear
  View Solution play_arrow

• question_answer148)
  Which of the following radiations has the least wavelength [AIEEE 2003]
  A)
             X-rays                                      done clear
  B)
             g-rays done clear
  C)
             b-rays                                      done clear
  D)
             a-rays done clear
  View Solution play_arrow

• question_answer149)
  A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is                                           [AIEEE 2003]
  A)
             0.8 In 2                                     done clear
  B)
             0.4 In 2 done clear
  C)
             0.2 In 2                                     done clear
  D)
             0.1 In 2 done clear
  View Solution play_arrow

• question_answer150)
  A nucleus with Z = 92 emits the following in a sequence: \[\alpha ,\,{{\beta }^{-}},\,{{\beta }^{-}},\,\alpha ,\alpha ,\alpha ,\alpha ,\alpha ,{{\beta }^{-}},\,{{\beta }^{-}},\alpha ,\,{{\beta }^{+}},\,{{\beta }^{+}},\,\alpha \]. The Z of the resulting nucleus is                                       [AIEEE 2003]
  A)
             74   done clear
  B)
             76 done clear
  C)
             78   done clear
  D)
             82 done clear
  View Solution play_arrow

• question_answer151)
  Radioactive nuclei that are injected into a patient collect at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called                              [AIIMS 2003]
  A)
             Gamma camera                   done clear
  B)
             CAT scan done clear
  C)
             Radiotracer technique done clear
  D)
             Gamma ray spectroscopy done clear
  View Solution play_arrow

• question_answer152)
  A radioactive decay chain starts from \[_{93}N{{p}^{237}}\] and produces \[_{90}T{{h}^{229}}\] by successive emissions. The emitted particles can be                                [MP PMT 2004]
  A)
             Two a-particles and one b-particle done clear
  B)
             Three \[{{\beta }^{+}}\] particles done clear
  C)
             One a particle and two \[{{\beta }^{+}}\] particles done clear
  D)
             One a particle and two \[{{\beta }^{-}}\] particles done clear
  View Solution play_arrow

• question_answer153)
  The half-life of a sample of a radioactive substance is 1 hour. If \[8\times {{10}^{10}}\] atoms are present at \[t=0\], then the number of atoms decayed in the duration \[t=2\] hour to \[t=4\] hour will be                                             [MP PMT 2004]
  A)
             \[2\times {{10}^{10}}\]     done clear
  B)
             \[1.5\times {{10}^{10}}\] done clear
  C)
             Zero                                           done clear
  D)
             Infinity done clear
  View Solution play_arrow

• question_answer154)
  Carbon dating is best suited for determining the age of fossils if their age in years is of the order of          [AIIMS 2004]
  A)
             \[{{10}^{3}}\]                        done clear
  B)
             \[{{10}^{4}}\] done clear
  C)
             \[{{10}^{5}}\]                        done clear
  D)
             \[{{10}^{6}}\] done clear
  View Solution play_arrow

• question_answer155)
  A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is [KCET 2004]
  A)
             120 min                                   done clear
  B)
             80 min done clear
  C)
             30 min                                      done clear
  D)
             20 min done clear
  View Solution play_arrow

• question_answer156)
  The half-life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after [CBSE PMT 2004]
  A)
             2400 years                              done clear
  B)
             3200 years done clear
  C)
             4800 years                              done clear
  D)
             6400 years done clear
  View Solution play_arrow

• question_answer157)
  Activity of radioactive element decreased to one third of original activity \[{{R}_{0}}\] in 9 years. After further 9 years, its activity will be                                                                    [DCE 2002]
  A)
             \[{{R}_{0}}\]                          done clear
  B)
             \[\frac{2}{3}{{R}_{0}}\] done clear
  C)
             \[{{R}_{0}}/9\]                      done clear
  D)
             \[{{R}_{0}}/6\] done clear
  View Solution play_arrow

• question_answer158)
  The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant                      [DPMT 2003]
  A)
             40 year, 0.9173/year          done clear
  B)
             90 year, 9.017/year done clear
  C)
             80 year, 0.0173 year           done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer159)
  The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days                                                             [Pb. PMT 2003]
  A)
             0.0019 mg                              done clear
  B)
             1.019 mg done clear
  C)
             1.109 mg                                 done clear
  D)
             0.019 mg done clear
  View Solution play_arrow

• question_answer160)
  A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days [AIIMS 2005]
  A)
             0.5  done clear
  B)
             0.25 done clear
  C)
             0.125                                        done clear
  D)
             0.33 done clear
  View Solution play_arrow

• question_answer161)
  Starting with a sample of pure \[^{66}Cu,\,\frac{7}{8}\] of it decays into Zn in 15 min. The corresponding half-life is                   [AIEEE 2005]
  A)
             5 min                                        done clear
  B)
             \[7\frac{1}{2}\] min done clear
  C)
             10 min                                      done clear
  D)
             15 min done clear
  View Solution play_arrow

• question_answer162)
  A radioactive material has a half-life of 8 years. The activity of the material will decrease to about 1/8 of its original value in                                                                                            [UPSEAT 2005]
  A)
             256 year                                  done clear
  B)
             128 year                                          done clear
  C)
             64 year                                    done clear
  D)
             24 year done clear
  View Solution play_arrow

• question_answer163)
  A nucleus decays by \[{{\beta }^{+}}\] emission followed by a gamma emission. If the atomic and mass numbers of the parent nucleus are Z and A respectively, the corresponding numbers for the daughter nucleus are respectively.  [UPSEAT 2005]
  A)
             \[Z-1\] and \[A-1\]             done clear
  B)
             \[Z+1\] and \[A\]                        done clear
  C)
             \[Z-1\] and \[A\]                 done clear
  D)
             \[Z+1\] and \[A-1\]                    done clear
  View Solution play_arrow

• question_answer164)
  \[_{90}^{232}Th\] an isotope of thorium decays in ten stages emitting six a-particles and four b-particles in all. The end product of the decay is                                               [CPMT 2005]
  A)
             \[_{82}^{206}Pb\]               done clear
  B)
             \[_{82}^{209}Pb\]                      done clear
  C)
             \[_{82}^{208}Pb\]               done clear
  D)
             \[_{83}^{209}Br\]                       done clear
  View Solution play_arrow

• question_answer165)
  The composition of an a-particle  can be expressed as [CPMT 2005]
  A)
             \[1P+1N\]                              done clear
  B)
             \[1P+2N\]                              done clear
  C)
             \[2P+1N\]                              done clear
  D)
             \[2P+2N\]                                      done clear
  View Solution play_arrow

• question_answer166)
  A nucleus of mass 218 amu in free state decays to emit an a-particle. Kinetic energy of the a-particle emitted is 6.7 MeV. The recoil energy (in MeV) of the daughter nucleus is [EAMCET 2005]
  A)
             1.0 done clear
  B)
             0.5  done clear
  C)
             0.25                                           done clear
  D)
             0.125                                        done clear
  View Solution play_arrow

• question_answer167)
  The particle that possesses half integral spin as [EAMCET 2005]
  A)
             Photon                                    done clear
  B)
             Pion                                                  done clear
  C)
             Proton                                     done clear
  D)
             K-meson                                 done clear
  View Solution play_arrow

• question_answer168)
  Nuclear fusion is common to the pair               [MP PMT 2005]
  A)
             Thermonuclear reactor, uranium based nuclear reactor done clear
  B)
             Energy production in sun, uranium based nuclear reactor                  done clear
  C)
             Energy production in sun, hydrogen bomb done clear
  D)
             Disintegration of heavy nuclei, hydrogen bomb                      done clear
  View Solution play_arrow

• question_answer169)
  \[{{C}^{14}}\] has half-life 5700 years. At the end of 11400 years, the actual amount left is                                            [MP PET 2005]
  A)
             0.5 of original amount       done clear
  B)
             0.25 of original amount            done clear
  C)
             0.125 of original amount          done clear
  D)
             0.0625 of original amount done clear
  View Solution play_arrow

• question_answer170)
  Mean life of a radioactive sample is 100 seconds. Then its half-life (in minutes) is                                               [KCET 2005]
  A)
             0.693                                        done clear
  B)
             1 done clear
  C)
             10-4                                            done clear
  D)
             1.155 done clear
  View Solution play_arrow

• question_answer171)
  \[_{86}{{A}^{222}}{{\to }_{84}}{{B}^{210}}\]. In this reaction how many \[\alpha \] and \[\beta \] particles are emitted                                                                 [BHU 2005]
  A)
             \[6\alpha ,\,3\beta \]        done clear
  B)
             \[3\alpha ,\,4\beta \] done clear
  C)
             \[4\alpha ,\,3\beta \]        done clear
  D)
             \[3\alpha ,\,6\beta \] done clear
  View Solution play_arrow

• question_answer172)
  The phenomenon of radioactivity is                        [BHU 2005]
  A)
             Exothermic change which increases or decreases with temperature done clear
  B)
             Increases on applied pressure done clear
  C)
             Nuclear process does not depend on external factors done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer173)
  If half-life of radium is 77 days. Its decay constant in day will be                                                  [BCECE 2005]
  A)
             \[3\times {{10}^{-13}}\]/day  done clear
  B)
             \[9\times {{10}^{-3}}\]/day done clear
  C)
             \[1\times {{10}^{-3}}\]/day    done clear
  D)
             \[6\times {{10}^{-3}}\]/day done clear
  View Solution play_arrow

• question_answer174)
  In a radioactive reaction \[_{92}{{X}^{232}}{{\to }_{82}}{{Y}^{204}}\], the number of \[\alpha -\]particles emitted is                                                                       [BCECE 2005]
  A)
             7     done clear
  B)
             6 done clear
  C)
             5     done clear
  D)
             4 done clear
  View Solution play_arrow

• question_answer175)
  In a sample of radioactive material, what fraction of the initial number of active nuclei will remain undisintegrated after half of a half-life of the sample         [Kerala PMT 2005]
  A)
             \[\frac{1}{4}\]                       done clear
  B)
             \[\frac{1}{2\sqrt{2}}\] done clear
  C)
             \[\frac{1}{\sqrt{2}}\]         done clear
  D)
             \[2\sqrt{2}\] done clear
  View Solution play_arrow

• question_answer176)
  Consider two nuclei of the same radioactive nuclide.  One of the nuclei was created in a supernova explosion 5 billion years ago. The other was created in a nuclear reactor 5 minutes ago. The probability of decay during the next time is                                                                                [KCET 2005]
  A)
             Different for each nuclei done clear
  B)
             Nuclei created in explosion decays first done clear
  C)
             Nuclei created in the reactor decays first done clear
  D)
             Independent of the time of creation done clear
  View Solution play_arrow