# Solved papers for NEET Physics Photo Electric Effect, X- Rays & Matter Waves NEET PYQ-Photo Electric Effect,X-Rays

### done NEET PYQ-Photo Electric Effect,X-Rays Total Questions - 52

• question_answer1) Light of wavelength $5000\overset{o}{\mathop{A}}\,$ falls on a sensitive plate with photoelectric work function of 1.9 eV. The kinetic energy of the photoelectron emitted will be:                                      [AIPMT 1998]

A)
0.58 eV

B)
2.48 eV

C)
1.48 eV

D)
2.68 eV

• question_answer2) In a photo-emissive cell, with exciting wavelength$\lambda ,$ the fastest electron has speed v. If the exciting wavelength is changed to $3\lambda /4,$ the speed of the fastest emitted electron will be :   [AIPMT 1998]

A)
$v\,{{(3/4)}^{1/2}}$

B)
$v\,{{(4/3)}^{1/2}}$

C)
less than $v\,{{(4/3)}^{1/2}}$

D)
greater than $v\sqrt{\frac{4}{3}}$

• question_answer3)             The photoelectric work function for a metal surface is 4.125 eV. The cut-off wavelength for this surface is: [AIPMT 1999]

A)
$4125\,\overset{o}{\mathop{A}}\,$

B)
$3000\,\overset{o}{\mathop{A}}\,$

C)
$6000\,\overset{o}{\mathop{A}}\,$

D)
$2062.5\,\overset{o}{\mathop{A}}\,$

• question_answer4) When intensity of incident light increases:                                                                           [AIPMT 1999]

A)
photo-current increases

B)
photo-current decreases

C)
kinetic energy of emitted photoelectrons increases

D)
kinetic energy of emitted photoelectrons decreases

• question_answer5) Einstein's work on photoelectric effect gives support to:                               [AIPMT 2000]

A)
$E=m{{c}^{2}}$

B)
$E=hv~$

C)
$hv=\frac{1}{2}m{{v}^{2}}$

D)
$E=\frac{h}{\lambda }$

• question_answer6) Which of the following phenomena exhibits particle's nature of light?             [AIPMT 2001]

A)
Interference

B)
Diffraction

C)
Polarisation

D)
Photoelectric effect

• question_answer7)                         A light source is at a distance d from a photoelectric cell, then the number of photoelectrons emitted from the cell is n. If the distance of light source and cell is reduced to half, then the number of photoelectrons emitted will become:                                                                                                                                                                    [AIPMT 2001]

A)
$\frac{n}{2}$

B)
2n

C)
4 n

D)
n

• question_answer8) In X-rays diffraction experiment distance between atomic lattice planes of diffraction grating is$2.8\times {{10}^{-10}}\,m,$ then the maximum wavelength of X-rays (in metre) is:                                                                 [AIPMT 2001]

A)
2.5

B)
$5.6\times {{10}^{-10}}$

C)
$4\times {{10}^{-10}}$

D)
$4.6\times {{10}^{-10}}$

• question_answer9) The following particles are moving with the same velocity, then maximum de-Broglie wavelength will be for:                                                                                                                                                                              [AIPMT 2002]

A)
proton

B)
$\alpha$-particle

C)
neutron

D)
$\beta$-particle

• question_answer10) When ultraviolet rays are incident on metal plate, the photoelectric effect does not occur. It occurs by incidence of:                                                                                                                                            [AIPMT 2002]

A)
infrared rays

B)
X-rays

C)

D)
light waves

• question_answer11) A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m  then:                                                                                                                                                  [AIPMT 2003]

A)
each emitted electron carries half the initial energy

B)
number of electrons emitted is a quarter of the initial number

C)
each emitted electron carries one quarter of the initial energy

D)
number of electrons emitted is half the initial number

• question_answer12) According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is:                                                                   [AIPMT (S) 2004]

A)

B)

C)

D)

• question_answer13) The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation of wavelength $4100\,\overset{o}{\mathop{A}}\,$ is/are:                                                                                                                                                   [AIPMT (S) 2005]

A)
none

B)
A only

C)
A and B only

D)
all the three metals

• question_answer14) A photosensitive metallic surface has work function, $h{{v}_{0}}$. If photons of energy $2\,h{{v}_{0}}$ fall on this surface, the electrons come out with a maximum velocity of $4\times {{10}^{6}}\,m/s$. When the photon energy is increased to $5\,h{{v}_{0}},$ then maximum velocity of photoelectrons will be:                                    [AIPMT (S) 2005]

A)
$2\times {{10}^{6}}m/s$

B)
$2\times {{10}^{7}}m/s~$

C)
$8\times {{10}^{5~}}m/s$

D)
$8\times {{10}^{6}}M/s$

• question_answer15) A photo-cell employs photoelectric effect to convert:                                          [AIPMT (S) 2006]

A)
change in the frequency of light into a change in electric voltage

B)
change in the intensity of illumination into change in photoelectric current

C)
change in the intensity of illumination into a change in the work function of the photocathode

D)
change in the frequency of light into a change in the electric current

• question_answer16) When photons of energy hv fall on an aluminium plate (of work function ${{E}_{0}}$), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of die ejected photoelectrons will be:                                                                                                                       [AIPMT (S) 2006]

A)
$K+{{E}_{0}}$

B)
2 K

C)
K

D)
$K+hv$

• question_answer17) The momentum of a photon of energy 1 MeV in kg m/s, will be:                        [AIPMT (S) 2006]

A)
$0.33\times {{10}^{6}}$

B)
$7\times {{10}^{-24}}$

C)
${{10}^{-22}}$

D)
$5\times {{10}^{-22}}$

• question_answer18) A 5W source emits monochromatic light of wavelength $5000\,\overset{o}{\mathop{A}}\,$. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of:                                                         [AIPMT (S) 2007]

A)
4

B)
8

C)
16

D)
2

• question_answer19) Monochromatic light of frequency $6.0\times {{10}^{14}}Hz$ is produced by a laser. The power emitted is $2\times {{10}^{-3}}W$. The number of photons emitted, on the average, by the source per second is: [AIPMT (S) 2007]

A)
$5\times {{10}^{15}}$

B)
$5\times {{10}^{16~}}$

C)
$5\times {{10}^{17}}$

D)
$5\times {{10}^{14}}$

• question_answer20) A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of $3\times {{10}^{6}}m{{s}^{-1}}$. The velocity of the Particle is                                                                       [AIPMPT (S) 2008]

A)
$2.7\times {{10}^{-18}}m{{s}^{-1}}$

B)
$9\times {{10}^{-2}}m{{s}^{-1}}$

C)
$3\times {{10}^{-31}}m{{s}^{-1}}\ D) \[2.7\times {{10}^{-21}}m{{s}^{-1}}$

• question_answer21) The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface, having work function $5.01\text{ }eV,$ when ultraviolet light of 200nm falls on it, must be                       [AIPMT (S) 2010]

A)
2.4 V

B)
$-1.2\text{ }V$

C)
2.4 V

D)
1.2 V

• question_answer22) When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectron and their maximum kinetic energy are N and T respectively. If the intensity of radiation is $2I,$ the number of emitted electrons and their maximum kinetic energy are respectively                                                                             [AIPMT (M) 2010]

A)
N and 2T

B)
2N and T

C)
2N and 2T

D)
N and T

• question_answer23) The threshold frequency for a photo-sensitive metal is$3.3\times {{10}^{14}}Hz$. If light of frequency $8.2\times {{10}^{14}}Hz$ is incident on this metal, the cut-off voltage for the photo-electric emission is nearly [AIPMT (M) 2011]

A)
2 V

B)
3 V

C)
5 V

D)
1 V

• question_answer24) An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength   so   emitted   illuminates   a photo-sensitive material having work function$2.75\text{ }eV$. If the stopping potential of the photo-electron is 10 V, the value of n is                                                                                                                [AIPMT (M) 2011]

A)
3

B)
4

C)
5

D)
2

• question_answer25) In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by             [AIPMT (S) 2011]

A)
Increasing the filament current

B)
Decreasing the filament current

C)
decreasing the potential difference between the anode and filament

D)
Increasing the potential difference between the anode and filament

• question_answer26) Photoelectric emission occurs only when the incident light has more than a certain minimum                 [AIPMT (S) 2011]

A)
wavelength

B)
intensity

C)
frequency

D)
power

• question_answer27) Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would                                                         [AIPMT (S) 2011]

A)
decrease by 2 times

B)
decrease by 4 times

C)
increase by 4 times

D)
increase by 2 times

• question_answer28) In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is                                            [AIPMT (S) 2011]

A)
1.3 V

B)
0.5 V

C)
2.3 V

D)
1.8 V

• question_answer29) If the momentum of an electron is changed by p, then the de-Broglie wavelength associated with it changes by 0.5%. The initial momentum of electron will be                                                                     [AIPMT (M) 2012]

A)
200 p

B)
400 p

C)
$\frac{p}{200}$

D)
100 p

• question_answer30) Two radiations of photon energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is                                  [AIPMT (M) 2012]

A)
1 : 4

B)
1 : 2

C)
1 : 1

D)
1 : 5

• question_answer31) A 200 W sodium street lamp emits yellow light of wavelength 0.6 um. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is                      [AIPMT (S) 2012]

A)
$1.5\times {{10}^{20}}$

B)
$6\times {{10}^{18}}$

C)
$62\times {{10}^{20}}$

D)
$3\times {{10}^{19}}$

• question_answer32) Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. The threshold frequency of the material is         [AIPMT (S) 2012]

A)
$\text{4 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{15}}}\,{{\text{H}}_{\text{Z}}}$

B)
$5\times {{10}^{15}}\,{{H}_{Z}}$

C)
$1.6\times {{10}^{15}}\,{{H}_{Z}}$

D)
$2.5\times {{10}^{15}}\,{{H}_{Z}}$

• question_answer33) An $\alpha$-particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of $0.25\text{ }Wb/{{m}^{2}}$. The de-Broglie wavelength associated with the particle will be                              [AIPMT (S) 2012]

A)
$1\overset{o}{\mathop{A}}\,$

B)
$0.1\overset{o}{\mathop{A}}\,$

C)
$10\overset{o}{\mathop{A}}\,$

D)
$0.01\overset{o}{\mathop{A}}\,$

• question_answer34) For photoelectric emission from certain metal the cut-off frequency is v. If radiation of frequency 2v impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is the electron mass)              [NEET 2013]

A)
$\sqrt{\frac{hv}{(2m)}}$

B)
$\sqrt{\frac{hv}{m}}$

C)
$\sqrt{\frac{2hv}{m}}$

D)
$\sqrt[2]{\frac{hv}{m}}$

• question_answer35) The wavelength ${{\lambda }_{e}}$ of an electron and ${{\lambda }_{p}}$ of a photon of same energy E are related by                                                                                                                                                [NEET 2013]

A)
${{\lambda }_{p}}\propto \lambda _{e}^{2}$

B)
${{\lambda }_{p}}\propto {{\lambda }_{e}}$

C)
${{\lambda }_{p}}\propto \sqrt{{{\lambda }_{e}}}$

D)
${{\lambda }_{p}}\propto \frac{1}{\sqrt{{{\lambda }_{e}}}}$

• question_answer36) Light with an energy flux of $25\times {{10}^{4}}W{{m}^{-2}}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15\,c{{m}^{2}},$ the average force exerted on the surface is              [NEET 2014]

A)
$1.25\times {{10}^{-6}}N$

B)
$2.50\times {{10}^{-6}}N$

C)
$1.20\times {{10}^{-6}}N$

D)
$3.0\times {{10}^{-6}}N$

• question_answer37) When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. 'The work function of the metal is                                         [NEET 2014]

A)
0.65 eV

B)
1.0 eV

C)
1.3 eV

D)
1.5 eV

• question_answer38) If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de-Broglie wavelength of the particle is                                                                          [NEET 2014]

A)
25

B)
75

C)
60

D)
50

• question_answer39) A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum on a transferred to the surface is (c = velocity of light)                                                                                                              [NEET  2015]

A)
$\frac{E}{c}$

B)
$\frac{2E}{c}$

C)
$\frac{2E}{{{c}^{2}}}$

D)
$\frac{E}{{{c}^{2}}}$

• question_answer40) A certain metallic surface is illuminated with monochromatic light of wavelength $\lambda$. The stopping potential for photoelectric current for this light is $3{{V}_{0}}$. If the same surface is illuminated with light of wavelength $2\,\lambda ,$ the stopping potential is ${{V}_{0}}$. The threshold wavelength for this surface for photoelectric effect is                [NEET  2015]

A)
$6\lambda$

B)
$4\lambda$

C)
$\frac{\lambda }{4}$

D)
$\frac{\lambda }{6}$

• question_answer41) Which of the following figures represent the variation of particle momentum and the associated de-Broglie wavelength? [NEET  2015]

A)

B)

C)

D)

• question_answer42) A photoelectric surface is illuminated successively by monochromatic light of wavelength$\lambda$ and$\frac{\lambda }{2}$. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is (A = Planck's constant, c = speed of light)                                                                         [NEET (Re) 2015]

A)
$\frac{hc}{2\lambda }$

B)
$\frac{hc}{\lambda }$

C)
$\frac{2hc}{\lambda }$

D)
$\frac{hc}{3\lambda }$

• question_answer43) Light of wavelength 500 nm is incident on a metal with work function 2.28 eV. The de-Broglie wavelength of the emitted electron is                                                                                              [NEET (Re) 2015]

A)
$<2.8\times {{10}^{-10}}m$

B)
$<2.8\times {{10}^{-9}}m$

C)
$\le 2.8\times {{10}^{-9}}m$

D)
$\le 2.8\times {{10}^{-12}}m$

• question_answer44) When a metallic surface is illuminated with radiation of wavelength $\lambda ,$ the stopping potential is V. If the same surface is illuminated with radiation of wavelength $2\lambda ,$ the stopping potential is $\frac{V}{4}$. The threshold wavelength for the metallic surface is :-                                                                                    [NEET - 2016]

A)
$4\lambda$

B)
$5\lambda$

C)
$\frac{5}{2}\lambda$

D)
$3\lambda$

• question_answer45) The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m, is                                                                                                                              [NEET-2017]

A)
$\frac{2h}{\sqrt{mkT}}$

B)
$\frac{h}{\sqrt{mkT}}$

C)
$\frac{h}{\sqrt{3mkT}}$

D)
$\frac{2h}{\sqrt{3mkT}}$

• question_answer46) The photoelectric threshold wavelength of silver is $3250\times {{10}^{-10}}m$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536\times {{10}^{-10}}m$ is                               [NEET-2017] (Given $h=4.14\times {{10}^{-15}}eVs$ and $c=3\times {{180}^{8}}\,m{{s}^{-1}}$)

A)
$\approx 0.3\times {{10}^{6}}\,m{{s}^{-1}}$

B)
$v=0.6\times {{10}^{6}}\,m/s$

C)
$\approx 0.6\times {{10}^{6}}\,m{{s}^{-1}}$

D)
$\approx 61\times {{10}^{3}}\,m{{s}^{-1}}$

• question_answer47) An electron of mass m with an initial velocity$\overrightarrow{v}={{v}_{0}}\widehat{i}({{v}_{0}}>0)$ enters an electric field $\overrightarrow{\text{E}}\text{=-}{{\text{E}}_{\text{0}}}\widehat{\text{i}}\text{(}{{\text{E}}_{\text{0}}}\text{=}$constant > 0) at t = 0. If ${{\lambda }_{0}}$ is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is                     [NEET - 2018]

A)
${{\lambda }_{\text{0}}}\text{t}$

B)
${{\lambda }_{0}}\left( 1+\frac{e{{E}_{0}}}{m{{V}_{0}}}t \right)$

C)
$\frac{{{\lambda }_{0}}}{\left( 1+\frac{e{{E}_{0}}}{m{{V}_{0}}}t \right)}$

D)
${{\lambda }_{0}}$

• question_answer48) When the light of frequency $2{{v}_{0}}$(where ${{v}_{0}}$ is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is ${{v}_{1}}$. When the frequency of the incident radiation is increased to $5{{v}_{0}}$, the maximum velocity of electrons emitted from the same plate is ${{v}_{2}}$. The ratio of ${{v}_{1}}$ to ${{v}_{2}}$ is                                                                                              [NEET - 2018]

A)
$4:1$

B)
$1:4$

C)
$1:2$

D)
$2:1$

• question_answer49) An electron is accelerated through a potential difference of 10,000 V. Its de Broglie wavelength is, (nearly): $({{m}_{e}}=9\times {{10}^{31}}kg)$                                                                                  [NEET 2019]

A)
$12.2\times {{10}^{14}}m$

B)
12.2 nm

C)
$12.2\times {{10}^{13}}m$

D)

• question_answer50) Light with an average flux of $20\text{ }W/c{{m}^{2}}$ falls on a non-reflecting surface at normal incidence having surface area $20\text{ }c{{m}^{2}}$. The energy received by the surface during time span of 1 minute is:    [NEET 2020]

A)
$12\times {{10}^{3}}J$

B)
$24\times {{10}^{3}}J$

C)
$48\times {{10}^{3}}J$

D)
$10\times {{10}^{3}}J$

• question_answer51) An electron is accelerated from rest through a potential difference of V volt. If the de Broglie wavelength of the electron is $1.227\times {{10}^{2}}nm$, the potential difference is:              [NEET 2020]

A)
${{10}^{2}}V$

B)
${{10}^{3}}V$

C)
${{10}^{4}}V$

D)
$10\,V$

• question_answer52) Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled? [NEET 2020]

A)
four times

B)
one-fourth

C)
zero

D)
doubled