JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank

done Critical Thinking Total Questions - 65

• question_answer1)
  An a-particle of 5 MeV energy strikes with a nucleus of uranium at stationary at an scattering angle of 180o. The nearest distance upto which a-particle reaches the nucleus will be of the order of                            [IIT 1981; AIEEE 2004]
  A)
             \[1\,\overset{o}{\mathop{A}}\,\]                                     done clear
  B)
             \[{{10}^{-10}}cm\] done clear
  C)
             \[{{10}^{-12}}cm\] done clear
  D)
             \[{{10}^{-15}}cm\] done clear
  View Solution play_arrow

• question_answer2)
  The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is [MNR 1994; MP PMT 1994]
  A)
             1/2 done clear
  B)
             2/137 done clear
  C)
             1/137                                        done clear
  D)
             1/237 done clear
  View Solution play_arrow

• question_answer3)
  In hydrogen atom, electron makes transition from n=4 to n=1 level. Recoil momentum of the H atom will be [MP PMT 1994]
  A)
             \[3.4\times {{10}^{-27}}N\text{-}\]sec                          done clear
  B)
             \[6.8\times {{10}^{-27}}N\text{-}\]sec done clear
  C)
             \[3.4\times {{10}^{-24}}N\text{-}\]sec                          done clear
  D)
             \[6.8\times {{10}^{-24}}N\text{-}\]sec done clear
  View Solution play_arrow

• question_answer4)
  A sodium atom is in one of the states labeled 'Lowest excited levels'. It remains in that state for an average time of 10?8 sec, before it makes a transition back to a ground state. What is the uncertainty in energy of that excited state
  A)
             6.56 ´ 10?8 eV                        done clear
  B)
             2 ´ 10?8 eV done clear
  C)
             10?8 eV                                     done clear
  D)
             8 ´ 10?8 eV done clear
  View Solution play_arrow

• question_answer5)
  An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is                                       [IIT 1995]
  A)
             79.0                                           done clear
  B)
             51.8 done clear
  C)
             49.2                                           done clear
  D)
             38.2 done clear
  View Solution play_arrow

• question_answer6)
  A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by [MP PET 1995; MP PMT 1997]
  A)
             \[1.05\times {{10}^{-34}}\]J-sec                                       done clear
  B)
             \[3.16\times {{10}^{-34}}\]J-sec done clear
  C)
             \[2.11\times {{10}^{-34}}\]J-sec                                       done clear
  D)
             \[4.22\times {{10}^{-34}}\]J-sec (Given Planck constant \[h=6.6\times {{10}^{-34}}J-\]sec) done clear
  View Solution play_arrow

• question_answer7)
  Hydrogen (H), deuterium , singly ionized helium \[(H{{e}^{+}})\]and doubly ionized lithium \[(Li)\] all have one electron around the nucleus. Consider n =2 to n = 1 transition. The wavelengths of emitted radiations are \[{{\lambda }_{1}},\ {{\lambda }_{2}},\ {{\lambda }_{3}}\]and \[{{\lambda }_{4}}\] respectively. Then approximately                                [KCET 1994]
  A)
              \[{{\lambda }_{1}}={{\lambda }_{2}}=4{{\lambda }_{3}}=9{{\lambda }_{4}}\] done clear
  B)
             \[4{{\lambda }_{1}}=2{{\lambda }_{2}}=2{{\lambda }_{3}}={{\lambda }_{4}}\] done clear
  C)
             \[{{\lambda }_{1}}=2{{\lambda }_{2}}=2\sqrt{2}{{\lambda }_{3}}=3\sqrt{2}{{\lambda }_{4}}\] done clear
  D)
             \[{{\lambda }_{1}}={{\lambda }_{2}}=2{{\lambda }_{3}}=3\sqrt{2}{{\lambda }_{4}}\] done clear
  View Solution play_arrow

• question_answer8)
  The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is of the order of  [AMU 1995]
  A)
             \[{{10}^{20}}\]                      done clear
  B)
             \[{{10}^{19}}\] done clear
  C)
             \[{{10}^{17}}\]                      done clear
  D)
             \[{{10}^{15}}\] done clear
  View Solution play_arrow

• question_answer9)
  Consider an electron \[(m=9.1\times {{10}^{-31}}kg)\] confined by electrical forces to move between two rigid walls separated by \[1.0\times {{10}^{-9}}\]metre, which is about five atomic diameters. The quantised energy value for the lowest stationary state is [ISM Dhanbad 1994]
  A)
             \[12\times {{10}^{-20}}Joule\]                                          done clear
  B)
             \[6.0\times {{10}^{-20}}Joule\] done clear
  C)
             \[6.0\times {{10}^{-18}}Joule\]                                         done clear
  D)
             6 Joule done clear
  View Solution play_arrow

• question_answer10)
  \[\alpha -\]particles of energy 400 KeV are bombarded on nucleus of\[_{82}Pb\]. In scattering of \[\alpha -\]particles, its minimum distance from nucleus will be                                                                 [RPET 1997]
  A)
             0.59 nm                                   done clear
  B)
             0.59 Å done clear
  C)
             5.9 pm                                     done clear
  D)
             0.59 pm done clear
  View Solution play_arrow

• question_answer11)
  In a hypothetical Bohr hydrogen, the mass of the electron is doubled. The energy \[{{E}_{0}}\]and the radius \[{{r}_{0}}\]of the first orbit will be (\[{{a}_{0}}\]is the Bohr radius)                                       [Roorkee 1992]
  A)
     \[{{E}_{0}}=-\ 27.2\ eV;\ {{r}_{0}}={{a}_{0}}/2\]                 done clear
  B)
             \[{{E}_{0}}=-\ 27.2\ eV;\ {{r}_{0}}={{a}_{0}}\] done clear
  C)
             \[{{E}_{0}}=-13.6\ eV;\ {{r}_{0}}={{a}_{0}}/2\]           done clear
  D)
             \[{{E}_{0}}=-13.6\ eV;\ {{r}_{0}}={{a}_{0}}\] done clear
  View Solution play_arrow

• question_answer12)
  What is the radius of iodine atom (at. no. 53, mass number 126)                                                [CBSE PMT 1993]
  A)
             \[2.5\times {{10}^{-11}}m\] done clear
  B)
             \[2.5\times {{10}^{-9}}m\] done clear
  C)
             \[7\times {{10}^{-9}}m\]  done clear
  D)
             \[7\times {{10}^{-6}}m\] done clear
  View Solution play_arrow

• question_answer13)
  If in Rutherford?s experiment, the number of particles scattered at \[{{90}^{o}}\]angle are 28 per min, then number of scattered particles at an angle \[{{60}^{o}}\] and \[{{120}^{o}}\] will be  [UPSEAT 1999]
  A)
             112/min, 12.5/min              done clear
  B)
             100/min, 200/min done clear
  C)
             50/min, 12.5/min                done clear
  D)
             117/min, 25/min done clear
  View Solution play_arrow

• question_answer14)
  A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in \[L{{i}^{++}}\] will be (Ionisation energy of hydrogen atom is 13.6eV)                                                                       [UPSEAT 1999]
  A)
             182.51 Å                                  done clear
  B)
             177.17 Å done clear
  C)
             142.25 Å                                  done clear
  D)
             113.74 Å done clear
  View Solution play_arrow

• question_answer15)
  The ionisation potential of H-atom is \[13.6\,V\]. When it is excited from ground state by monochromatic radiations of \[970.6\,{AA}\], the number of emission lines will be (according to Bohr?s theory)                                          [RPET 1999]
  A)
  10   done clear
  B)
  8 done clear
  C)
  6     done clear
  D)
  4 done clear
  View Solution play_arrow

• question_answer16)
  A neutron with velocity V strikes a stationary deuterium atom, its kinetic energy changes by a factor of [DCE 2000]
  A)
             \[\frac{15}{16}\]                  done clear
  B)
             \[\frac{1}{2}\] done clear
  C)
             \[\frac{2}{1}\]                       done clear
  D)
             None of these                      done clear
  View Solution play_arrow

• question_answer17)
  Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Boh?r atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength l (given in terms of the Rydberg constant R for the hydrogen atom) equal to  [IIT-JEE (Screening) 2000]
  A)
             9/(5R)                                      done clear
  B)
             36/(5R) done clear
  C)
             18/(5R)                                    done clear
  D)
             4/R done clear
  View Solution play_arrow

• question_answer18)
  The transition from the state \[n=4\] to \[n=3\] in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition         [IIT-JEE (Screening) 2001]
  A)
             \[2\to 1\]                                done clear
  B)
             \[3\to 2\] done clear
  C)
             \[4\to 2\]                                done clear
  D)
             \[5\to 4\] done clear
  View Solution play_arrow

• question_answer19)
  An electron passing through a potential difference of 4.9 V collides with a mercury atom and transfers it to the first excited state. What is the wavelength of a photon corresponding to the transition of the mercury atom to its normal state                                                                        [AMU (Med.) 2002]
  A)
             2050 Å                                      done clear
  B)
             2240 Å done clear
  C)
             2525 Å                                      done clear
  D)
             2935 Å done clear
  View Solution play_arrow

• question_answer20)
  In the Bohr model of the hydrogen atom, let R, v and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n        [Pb. PET 2001; KCET 2002]
  A)
             R/E done clear
  B)
             E/v done clear
  C)
             RE   done clear
  D)
             vR done clear
  View Solution play_arrow

• question_answer21)
  A Hydrogen atom and a \[L{{i}^{++}}\] ion are both in the second excited state. If \[{{l}_{H}}\] and \[{{l}_{Li}}\] are their respective electronic angular momenta, and \[{{E}_{H}}\] and \[{{E}_{Li}}\] their respective energies, then          [IIT-JEE (Screening) 2002]
  A)
             \[{{l}_{H}}>{{l}_{Li}}\,\text{ and }|{{E}_{H}}|>|{{E}_{Li}}|\]               done clear
  B)
             \[{{l}_{H}}={{l}_{Li}}\text{ and }|{{E}_{H}}|<|{{E}_{Li}}|\] done clear
  C)
             \[{{l}_{H}}={{l}_{Li}}\text{ and }|{{E}_{H}}|>|{{E}_{Li}}|\]  done clear
  D)
             \[{{l}_{H}}<{{l}_{Li}}\text{ and }|{{E}_{H}}|<|{{E}_{Li}}|\] done clear
  View Solution play_arrow

• question_answer22)
  Which of the following atoms has the lowest ionization potential                                              [AIEEE 2003]
  A)
             \[_{8}^{16}O\]                     done clear
  B)
             \[_{7}^{14}N\] done clear
  C)
             \[_{55}^{133}Cs\]               done clear
  D)
             \[_{18}^{40}Ar\] done clear
  View Solution play_arrow

• question_answer23)
  The wavelengths involved in the spectrum of deuterium \[(_{1}^{2}D)\] are slightly different from that of hydrogen spectrum, because                                                       [AIEEE 2003]
  A)
             The attraction between the electr on and the nucleus is different in the two cases done clear
  B)
             The size of the two nuclei are different done clear
  C)
             The nuclear forces are different in the two cases done clear
  D)
             The masses of the two nuclei are different done clear
  View Solution play_arrow

• question_answer24)
  The electric potential between a proton and an electron is given by \[V={{V}_{0}}\ln \frac{r}{{{r}_{0}}},\] where \[{{r}_{0}}\] is a constant. Assuming Bohr?s model to be applicable, write variation of \[{{r}_{n}}\] with n, n being the principal quantum number   [IIT-JEE (Screening) 2003]
  A)
             \[{{r}_{n}}\propto n\]       done clear
  B)
             \[{{r}_{n}}\propto 1/n\] done clear
  C)
             \[{{r}_{n}}\propto {{n}^{2}}\]                                            done clear
  D)
             \[{{r}_{n}}\propto 1/{{n}^{2}}\] done clear
  View Solution play_arrow

• question_answer25)
  If the atom \[_{100}F{{m}^{257}}\] follows the Bohr model and the radius of \[_{100}F{{m}^{257}}\] is n times the Bohr radius, then find n                                                                                       [IIT-JEE (Screening) 2003]
  A)
             100 done clear
  B)
             200 done clear
  C)
             4     done clear
  D)
             \[\frac{1}{4}\] done clear
  View Solution play_arrow

• question_answer26)
  The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is \[1.4\ kilowatt/{{m}^{2}}\].The average earth- sun distance is \[1.5\times {{10}^{11}}metres\]. The mass lost by the sun per day is (1 day = 86400 seconds)                               [MP PMT 1993, 2003]
  A)
             \[4.4\times {{10}^{9}}kg\]       done clear
  B)
             \[7.6\times {{10}^{14}}kg\] done clear
  C)
             \[3.8\times {{10}^{12}}kg\]    done clear
  D)
             \[3.8\times {{10}^{14}}kg\] done clear
  View Solution play_arrow

• question_answer27)
  The binding energy per nucleon of \[{{O}^{16}}\]is 7.97 MeV and that of \[{{O}^{17}}\]is 7.75 MeV. The energy (in MeV)            required to remove a neutron from \[{{O}^{17}}\]is             [IIT 1995]
  A)
             3.52                                           done clear
  B)
             3.64 done clear
  C)
             4.23                                           done clear
  D)
             7.86 done clear
  View Solution play_arrow

• question_answer28)
  The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be                                                              [MP PET 1996]
  A)
             0.026 MeV                              done clear
  B)
             0.051 MeV done clear
  C)
             0.079 MeV                              done clear
  D)
             0.105 MeV done clear
  View Solution play_arrow

• question_answer29)
  Let \[{{m}_{p}}\]be the mass of a proton, \[{{m}_{n}}\]the mass of a neutron, \[{{M}_{1}}\]the mass of a \[_{10}^{20}Ne\] nucleus and \[{{M}_{2}}\]the mass of a \[_{20}^{40}Ca\]nucleus. Then                                  [IIT 1998; DPMT 2000]
  A)
             \[{{M}_{2}}=2{{M}_{1}}\]        done clear
  B)
             \[{{M}_{2}}>2{{M}_{1}}\] done clear
  C)
             \[{{M}_{2}}<2{{M}_{1}}\]        done clear
  D)
             \[{{M}_{1}}<10({{m}_{n}}+{{m}_{p}})\] done clear
  View Solution play_arrow

• question_answer30)
  A heavy nucleus at rest breaks into two fragments which fly off with velocities in the ratio 8 : 1. The ratio of radii of the fragments is                                                      [EAMCET (Engg.) 2001]
  A)
             1 : 2 done clear
  B)
             1 : 4 done clear
  C)
             4 : 1                                           done clear
  D)
             2 : 1 done clear
  View Solution play_arrow

• question_answer31)
  For uranium nucleus how does its mass vary with volume                    [IIT-JEE (Screening) 2003]
  A)
             \[m\propto V\]                    done clear
  B)
             \[m\propto 1/V\] done clear
  C)
             \[m\propto \sqrt{V}\]      done clear
  D)
             \[m\propto {{V}^{2}}\] done clear
  View Solution play_arrow

• question_answer32)
  A star initially has \[{{10}^{40}}\] deuterons. It produces energy via the processes            \[_{1}{{H}^{2}}{{+}_{1}}{{H}^{2}}{{\to }_{1}}{{H}^{3}}+p\]            \[_{1}{{H}^{2}}{{+}_{1}}{{H}^{3}}{{\to }_{2}}H{{e}^{4}}+n\]            The masses of the nuclei are as follows :            \[M({{H}^{2}})=2.014\ amu;\ M(p)=1.007\ amu;\]            \[M(n)=1.008\ amu;\ M(H{{e}^{4}})=4.001\ amu\]            If the average power radiated by the star is \[{{10}^{16}}W\],the deuteron supply of the star is exhausted in a time of the order of                                                                          [IIT 1993]
  A)
             \[{{10}^{6}}\]sec                  done clear
  B)
             \[{{10}^{8}}\]sec done clear
  C)
             \[{{10}^{12}}\]sec               done clear
  D)
             \[{{10}^{16}}\]sec done clear
  View Solution play_arrow

• question_answer33)
  The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilate, they produce gamma-rays of wavelength(s)                    [UPSEAT 2002]
  A)
             0.012 Å                                    done clear
  B)
             0.024 Å done clear
  C)
             0.012 Å to ¥                          done clear
  D)
             0.024 Å to ¥ done clear
  View Solution play_arrow

• question_answer34)
  In the nuclear fusion reaction \[_{1}^{2}H+_{1}^{3}H\to _{2}^{4}He+n,\] given that the repulsive potential energy between the two nuclei is \[-7.7\times {{10}^{-14}}J\], the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann?s constant \[k=1.38\times {{10}^{-23}}J/K\]] [AIEEE 2003]
  A)
             \[{{10}^{9}}K\]                     done clear
  B)
             \[{{10}^{7}}K\] done clear
  C)
             \[{{10}^{5}}K\]                     done clear
  D)
             \[{{10}^{3}}K\] done clear
  View Solution play_arrow

• question_answer35)
  A nucleus with mass number 220 initially at rest emits an a-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the a-particle [IIT JEE (Screening) 2003]
  A)
             4.4 MeV                                  done clear
  B)
             5.4 MeV done clear
  C)
             5.6 MeV                                  done clear
  D)
             6.5 MeV done clear
  View Solution play_arrow

• question_answer36)
  The half life of radioactive Radon is 3.8 days. The time at the end of which \[1/{{20}^{th}}\]of the Radon sample will remain undecayed is            (Given\[{{\log }_{10}}e=0.4343\])                                                                 [IIT 1981]
  A)
             3.8 days                                  done clear
  B)
             16.5 days done clear
  C)
             33 days                                    done clear
  D)
             76 days done clear
  View Solution play_arrow

• question_answer37)
  If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately                                                                         [MNR 1987]
  A)
             60%                                           done clear
  B)
             65% done clear
  C)
             70%                                           done clear
  D)
             75% done clear
  View Solution play_arrow

• question_answer38)
  A radioactive isotope X with a half-life of \[1.37\times {{10}^{9}}\] years decays to Y which is stable. A sample of rock from the moon was found to contain both the elements X and Y which were in the ratio of 1 : 7. The age of the rock is
  A)
             \[1.96\times {{10}^{8}}\]years                                          done clear
  B)
             \[3.85\times {{10}^{9}}\]years done clear
  C)
             \[4.11\times {{10}^{9}}\]years                                          done clear
  D)
             \[9.59\times {{10}^{9}}\]years done clear
  View Solution play_arrow

• question_answer39)
  From a newly formed radioactive substance (Half life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is [IIT 1983; SCRA 1996; DCE 2000; DPMT 2005]
  A)
             6 hours                                    done clear
  B)
             12 hours done clear
  C)
             24 hours                                  done clear
  D)
             128 hours done clear
  View Solution play_arrow

• question_answer40)
  The half life of radium is 1620 years and its atomic weight is 226 kgm per kilomol. The number of atoms that will decay from its 1 gm sample per second will be [MP PMT 1993; BVP 2003]
  A)
             \[3.61\times {{10}^{10}}\]       done clear
  B)
             \[3.6\times {{10}^{12}}\]  done clear
  C)
             \[3.11\times {{10}^{15}}\]       done clear
  D)
             \[31.1\times {{10}^{15}}\] (Avogadro's number \[N=6.02\times {{10}^{26}}\]atom/kilomol) done clear
  View Solution play_arrow

• question_answer41)
  A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is              [IIT 1995; UPSEAT 2002]           
  A)
             1080                                          done clear
  B)
             2430 done clear
  C)
             3240                                          done clear
  D)
             4860 done clear
  View Solution play_arrow

• question_answer42)
  A freshly prepared radioactive sample of half- life 1 hour emits radiations that are 128 times as intense as the permissible safe limit. The minimum time after which this sample can be safely used is                                           [KCET 1996]
  A)
             14 hours                                  done clear
  B)
             7 hours done clear
  C)
             128 hours                               done clear
  D)
             256 hours done clear
  View Solution play_arrow

• question_answer43)
  The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then                    [IIT 1999; UPSEAT 2003]
  A)
             X and Y have the same decay rate initially done clear
  B)
             X and Y decay at the same rate always done clear
  C)
             Y will decay at a faster rate than X done clear
  D)
             X will decay at a faster rate than Y done clear
  View Solution play_arrow

• question_answer44)
  For a substance the average life for a-emission is 1620 years and for b emission is 405 years. After how much time the 1/4 of the material remains after a and b emission                    [RPET 1999]
  A)
             1500 years                              done clear
  B)
             300 years done clear
  C)
             449 years                                done clear
  D)
             810 years done clear
  View Solution play_arrow

• question_answer45)
  The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is                                                      [Roorkee 1999]
  A)
             2000                                          done clear
  B)
             3000 done clear
  C)
             4000                                          done clear
  D)
             5000 done clear
  View Solution play_arrow

• question_answer46)
  A radioactive nucleus undergoes a-emission to form a stable element. What will be the recoil velocity of the daughter nucleus if V is the velocity of a-emission and A is the atomic mass of radioactive nucleus                               [DCE 2000; AIIMS 2004]
  A)
             \[\frac{4V}{A-4}\]               done clear
  B)
             \[\frac{2V}{A-4}\] done clear
  C)
             \[\frac{4V}{A+4}\]              done clear
  D)
             \[\frac{2V}{A+4}\] done clear
  View Solution play_arrow

• question_answer47)
  Half-life of a radioactive substance is 20 minutes. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately         [AIIMS 2000]                                    
  A)
             10 min                                      done clear
  B)
             20 min done clear
  C)
             30 min                                      done clear
  D)
             40 min done clear
  View Solution play_arrow

• question_answer48)
  Two radioactive materials \[{{X}_{1}}\] and \[{{X}_{2}}\] have decay constants \[10\lambda \] and \[\lambda \] respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of \[{{X}_{1}}\] to that of \[{{X}_{2}}\] will be \[1/e\] after a time                    [IIT-JEE (Screening) 2000]
  A)
             \[1/(10\lambda )\]             done clear
  B)
             \[1/(11\lambda )\] done clear
  C)
             \[11/(10\lambda )\] done clear
  D)
             \[1/(9\lambda )\] done clear
  View Solution play_arrow

• question_answer49)
   A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is                     [UPSEAT 2003]
  A)
             6.62 years                               done clear
  B)
             5 years done clear
  C)
             3.2 years                                 done clear
  D)
             7 years done clear
  View Solution play_arrow

• question_answer50)
  Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be                [KCET 2003]
  A)
             20 minutes                             done clear
  B)
             40 minutes done clear
  C)
             30 minutes                             done clear
  D)
             25 minutes done clear
  View Solution play_arrow

• question_answer51)
  After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is [IIT-JEE (Screening) 2004]
  A)
             6000                                          done clear
  B)
             9000 done clear
  C)
             3000                                          done clear
  D)
             24000 done clear
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• question_answer52)
  Excitation energy of a hydrogen like ion in its first excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is                                             [KCET 2004]
  A)
             54.4 eV                                    done clear
  B)
             13.6 eV done clear
  C)
             40.8 eV                                    done clear
  D)
             27.2 eV done clear
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• question_answer53)
  The rate of disintegration was observed to be \[{{10}^{17}}\] disintegrations per sec when its half life period is 1445 years. The original number of particles are                   [Pb. PET 2001]
  A)
             \[8.9\times {{10}^{27}}\] done clear
  B)
             \[6.6\times {{10}^{27}}\] done clear
  C)
             \[1.4\times {{10}^{16}}\] done clear
  D)
             \[1.2\times {{10}^{17}}\] done clear
  View Solution play_arrow

• question_answer54)
  An atomic power nuclear reactor can deliver 300 MW. The energy released due to fission of each nucleus of uranium atom \[{{U}^{238}}\] is 170 MeV. The number of uranium atoms fissioned per hour will be       [Pb. PET 2004; Kerala PET 2005]
  A)
             \[30\times {{10}^{25}}\]   done clear
  B)
             \[4\times {{10}^{22}}\] done clear
  C)
             \[10\times {{10}^{20}}\]   done clear
  D)
             \[5\times {{10}^{15}}\] done clear
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• question_answer55)
  The first excited state of hydrogen atom is 10.2 eV above its ground state. The temperature is needed to excite hydrogen atoms to first excited level, is                                [Pb. PET 2003]
  A)
             \[7.9\times {{10}^{4}}K\] done clear
  B)
             \[3.5\times {{10}^{4}}K\] done clear
  C)
             \[5.8\times {{10}^{4}}K\] done clear
  D)
             \[14\times {{10}^{4}}K\] done clear
  View Solution play_arrow

• question_answer56)
  A small quantity of solution containing Na24 radio nuclide of activity 1 microcurie is injected into the blood of a person. A sample of the blood of volume 1 cm3 taken after 5 hours shows an activity of 296 disintegration per minute. What will be the total volume of the blood in the body of the person. Assume that the radioactive solution mixes uniformly in the blood of the person (Take 1 curie = 3.7 ´ 1010 disintegration per second and \[{{e}^{-\lambda t}}=0.7927;\] where l = disintegration constant)
  A)
             5.94 litre                                  done clear
  B)
             2 litre done clear
  C)
             317 litre                                   done clear
  D)
             1 litre done clear
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• question_answer57)
  A hydrogen like atom of atomic number Z is in an excited state of quantum number 2n. It can emit a maximum energy photon of 204 eV. If it makes a transition to quantum state n, a photon of energy 40.8 eV is emitted. The value of  n will be                   [Based onIIT-JEE (Mains) 2000]
  A)
             1     done clear
  B)
             2 done clear
  C)
             3     done clear
  D)
             4 done clear
  View Solution play_arrow

• question_answer58)
  A radioactive sample of U238 decay to Pb through a process for which half life is 4.5 ´ 109 years. The ratio of number of nuclei of Pb to U238 after a time  of 1.5 ´ 109 years (given 21/3 = 1.26)        [Based on IIT-JEE (Mains) 2004]
  A)
             0.12                                           done clear
  B)
             0.26 done clear
  C)
             1.2  done clear
  D)
             0.37 done clear
  View Solution play_arrow

• question_answer59)
  The wavelength Ka X-rays produced by an X-ray tube is 0.76 Å. The atomic number of anticathode material is
  A)
             82   done clear
  B)
             41 done clear
  C)
             20   done clear
  D)
             10 done clear
  View Solution play_arrow

• question_answer60)
  Consider a hydrogen like atom  whose energy  in nth exicited state is given by \[{{E}_{n}}=-\frac{13.6{{Z}^{2}}}{{{n}^{2}}}\] when this excited atom makes a transition from excited state to ground state, most energetic photons have energy Emax = 52.224 eV and least energetic photons have energy Emin = 1.224 eV. The atomic number of atom is
  A)
             2     done clear
  B)
             5 done clear
  C)
             4     done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer61)
  A radioactive sample is a-emitter with half life 138.6 days is observed by a student to have 2000 disintegration/sec. The number of radioactive nuclei for given activity are
  A)
             3.45 ´ 1010                              done clear
  B)
             1 ´ 1010 done clear
  C)
             3.45 ´ 1015                                 done clear
  D)
             2.75 ´ 1011 done clear
  View Solution play_arrow

• question_answer62)
  A radioactive nucleus is being produced at a constant rate a per second. Its decay constant is l. If N0 are the number of nuclei at time t = 0, then maximum number of nuclei possible are
  A)
             \[\frac{\alpha }{\lambda }\]   done clear
  B)
             \[{{N}_{0}}+\frac{\alpha }{\lambda }\] done clear
  C)
             N0   done clear
  D)
             \[\frac{\lambda }{\alpha }+{{N}_{0}}\] done clear
  View Solution play_arrow

• question_answer63)
  The ratio of radii of nuclei \[_{13}A{{l}^{27}}\] and \[_{52}{{X}^{A}}\] is 3 : 5. The number of neutrons in the nuclei of X will be
  A)
             52   done clear
  B)
             73 done clear
  C)
             125                                            done clear
  D)
             13 done clear
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• question_answer64)
  If one starts with one curie of radioactive substance (T1/2 = 12 hrs) the activity left after a period of 1 week will be about 
  A)
             1 curie                                      done clear
  B)
             120 micro curie done clear
  C)
             60 micro curie                       done clear
  D)
             8 mili curie done clear
  View Solution play_arrow

• question_answer65)
  Rest mass energy of an electron is 0.54 MeV. If velocity of the electron is 0.8 c, then K.E. of the electron is
  A)
             0.36 MeV done clear
  B)
             0.41 MeV done clear
  C)
             0.48 MeV                                done clear
  D)
             1.32 MeV done clear
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