Photoelectric Effect Questions and Answers

32 ALLE When the energy of the incident radiation is incredased 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 1 0 65 eV 3 1 3 eV 2 1 0 eV 4 1 5 all

The stopping potential is 4 Vwhen wavelength of incident monochromatic radiation is If wavelength of incident radiation is doubled on same photosensitive material the stopping potential becomes V The threshold wavelength of the photosensitive material is Only one correct answer A B 100 D X C 3A X

When a metallic surface is illuminated by a light of frequency 8 10 4 Hz photoelectron of maximum energy 0 5eV is emitted When the same surface is illuminated by light of frequency 12 10 4 Hz photoelectron of maximum energy 2eV is emitted The work function is in eV

If all the particles are moving with same velocity then maximum de Broglie wavelength will be for Neutron O Proton hr min B particle

Ultraviolet radiation of 6 2 eV falls on an aluminium surface work function 4 2 eV The kinetic energy in joules of the fastest emitted electron is approximately O 3 2 x 10 21 3 2 10 19 hr mi 3 2 x 10 17

The graph in the broken line represents one for a given freq and intensity of the incident radiatio freq is increased and the intensity is reduced which of the following graphs of unbroken line repres new situation Where V in the variable potential diff of the source applied across the photo electric graph is plotted between variable p d and photo electric current Current A A A A B B C C D E P d V D D

The stopping potential is 4V when wavelength of incident monochromatic radiation is X If wavelength of incident radiation is doubled on same photosensitive material the stopping potential becomes V The threshold wavelength of the photosensitive material is Only one correct answer B i

7 Initially a photon of wavelength falls on a photocathode and emits an electron of maximum energy E If the wavelength of the incident photon is changed to 22 the maximum energy of the emitted electron becomes E2 The value of hC is h planck s constant and C speed of light 2 2 E E E E 2 1 2 2 2 2 3 E E 2 4 21 22 E2 E

In photoelectric experiment both sodium work function 2 3 eV and tungsten work functio 4 5 eV were illuminated by an ultraviolet light of same wavelength If the stopping potent of tungsten is measured to be 1 8 V the value of the stopping potential for sodium will be A 4 V B 4 2 V C D 3 4 V 4 3 V

38 An image of the sun is formed by a lens of focal length 30 cm on the metal surface of a photo electric cell and it produces a current I The lens forming the image is then replaced by another lens of the same diameter but of focal length 15 cm The photoelectric current this case will be In both cases the plate is kept at focal plane and normal to the axis lens 2 21 1 1 2 3 I 4 41

Why maximum kinetic energy The elec trons can be ejected from the surface a toms as well as the inner layer atoms However the probability of ejection of e lectrons from the surface is higher as t hey get more energy for emission of ele ctrons Thus we consider the maximu m kinetic energy The energy of electro ns decreases when they are struck by a gas particle present in the discharge tu be which cannot be predicted experim entally Hence we always deal with ma ximum kinetic energy

The threshold frequency for a certain photosensitive metal is vo When it is illuminated by light of frequency v 200 the maximum velocity of photoelectrons is vo What will be the maximum velocity of the photoelectrons when the same metal is illuminated by light of frequency v 5v0 O 2vo 0 240 O 2 2vo 0440 Marks 4 1

In an isolated Li electron jumps from n 2 to n 1 What is the recoil momentum of the ion in kg m s 1 5 44 x 10 27 3 16 32 10 27 2 48 96 10 27 4 8 16 10 27 If n 1 is taken to be reference of the potential energy what will be the kinetic energy in eV of an electro

2 Figure shows some energy levels of an atom If the transition E to E gives emission of ultraviolet radiatio which of the following transitions could give infra red radiation 13 1 E to E 3 E to E If the ga E 0 85 eV E 1 5 eV E 2 7 eV E 3 6 eV 2 E to E 4 E to E E Foundations in 017 A

4 Statement I When ultraviolet light is incident on a photocell its stopping potential is Vo and the maximum kinetic energy of the photoelectrons is Kmax When the ultraviolet light is replaced by X rays both Vo and Kmax increase Statement II Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light

3 A light of frequency 10 0 Hz is incident on a photosensitive material The given frequency is 2 5 times of Threshold frequency If above incident frequency is made one third and intensity made five times the photocurrent becomes 1 Five times the initial photocurrent 2 One third the initial photocurrent 3 Three times the initial photocurrent 4 Zero

When a centimeter thick surface is illuminated with light of wavelength A stopping potential is V when the same surface is illuminated by light of wavelength 2A stopping potential is 3 Threshold wavelength for metallic surface is

n photoelectric effect the saturation photocurrent Depends both on intensity and frequency of the incident light Increase with increase in frequency of incident light Decreases with increase in frequency of incident light Does not depend on the frequency of incident light but depends on the intensity of incident light

Which of the following statement is incorrect about photo electric effect It is based on particle nature of light Stopping potential depends on the intensity of incident light having fixed frequency Saturation current depends on the intensity of incident light having fixed frequency Frequency should be greater than threshold frequency for emission of electrons

The radiation corresponding to 32 transition of hydro gen atom falls on a metal surface to produce photoelectrons These electrons are made to enter a magnetic field of 3x10 T If the radius of the largest circular path following by these electrons is 10 0 mm the work function of the metal is close to a 1 6 eV c 1 1 eV b 1 8 eV d 0 8 eV

Given that the density of states related effective masses of electrons and holes in Si are approximately 1 08 m and 0 56 m respectively and the electron and hole drift mobility at room temperature are 1350 and 450 cm V s respectively Calculate the intrinsic concentration and intrinsic resistivity of Si

In a given N type Si material if donor concentration is one atom per 2 108 silicon atoms Assuming that effective mass of electron is equal to its true mass Find the value of temperature at which Fermi level coincides with the edge of conduction band density of atoms in Si is 5 1028 atoms per m 5x1028

Work function of two metal surfaces are 2 0 eV and 3 0 eV Both are illuminated by light energy of incident photons greater than 3 eU If graph is plotted between maximum kinetic energy and frequency for both surfaces then slope of the graphs are in the ratio Only one correct answer 9 2 3 B 3 2 C 7 1

In the vacuum tube experiment with perfora ted anode what will happen to the emitted e lectrons after hitting the phosphor material How the electrical neutrality is maintained Also in anode how the electrical neutrality is maintained Sir Can you please clear my dou

If the frequency and intensity of a light source are both 2 doubled Now consider the following statements A The saturation photocurrent remains almost the same B the maximum kinetic energy of the photo electrons is doubled C The maximum kinetic energy of the photoelectrons is increased but not doubled The correct statement s is are 1 B only 3 A and C only 2 A and B only 4 C only

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 the electron will be 1 200p 2 400p 3 P

Consider the wavelength of the light is 383 nm The photo electrons are emitted from the surface of the specific metal when the light is falling on its surface Calculate the maximum kinetic energy of these electrons when the work function of the metal is 1 50 eV A 3 5 eV B 2 36 eV C 1 36 eV D 1 74 eV Answer

The threshold frequency for a photosensitive metal is 3 3 1014 Hz If light of frequency 8 2 1014 Hz is incident on this metal the cut off voltage for the photoelectric emission is nearly 1 5 V 3 21 AIPMT Mains 2011 2 1 V 4 21

A photosensitive metallic surface has work function hvo If photons of energy 2hv fall on this surface the electrons come out with a maximum velocity of 4 x 106 m s When the photon energy is increased to 5hv then maximum velocity of photoelectrons will be AIPMT Prelims 2005 2 2 107 m s 4 8 x 106 m s 1 2 x 106 m s 3 8 x 105 m s

hydrogen atom If the ionisation potential in the ground state for hydrogen is 13 6 e V then find the excitation potential of third orbit hit to ground state of hydrogen atom then calculate the wavelength of

Threshold wavelength for sodium is 6 x 10 7 m Then photoemission occurs for light of waveleng if 1 6 x 10 7 metre 2 6 x 10 7 metre 3 5 x 1014 metre A Frequency 5 x 1014 Hz

If the frequency of light incident on a metallic plate be doubled how will the maximum kinetic energy of the photoelectrons change 1 It becomes more than double 2 It becomes less than double 3 It becomes exactly double 4 It does not change work funct saturation I and I then as 1 4 2 4 3 4 4 4 Tower 8 Pu

A monochromatic point source of light is placed at a distance d from a metal surface Photo electrons are ejected at a rate n per second and with maximum kinetic energy E If the source is brought nearer to distance d 2 the rate and the maximum kinetic energy per photoelectron become nearly 1 2n and 2E 2 4n and 4E 3 4n and E 4 C

The cathode of a photocell Is work function changes from w to w w If the saturation currents before and after the change are I and 2 and all other conditions are unchanged then assuming hv W 1 2 2 1 3 1 12

The work function of a substance is 4eV The longest wavelength of light that can cause the emission of photoelectrons from this substance is approximately 1 540 nm 2 400 nm 3 310 nm 0 220 pm

9 If the threshold wavelength for a metal is 6200 A then minimum energy required to eject an electron from the surface of metal is nearly 1 1 eV NCERT Pg 394 2 2 eV 4 08 eV

When a metallic surface is illuminated with light of wavelength the stopping potential is x volt When the same surface is illuminated by light of X 3 wavelength 22 the stopping potential is Threshold wavelength for the metallic surface is 1 42 m 3 61 2 42 4 8 3

2 Given that a photon of light of wavelength 10000 has energy 1 23 eV Now when light of intensity and wavelength 5000 falls on a photo cell the saturation current and stopping potential are 0 40 A and 1 36 V respectively The work function is 1 0 43 eV 2 1 10 eV 3 1 36 eV motallic plate 18

5 When photon of energy 3 8 eV falls on metallic surface of work function 2 8 eV then the kinetic energy of emitted electrons are 1 1 eV 3 0 to 1 eV 2 6 6 eV 4 2 8 eV

Y An electron is to be accelerated from a velocity of 1 00x10 m s to a velocity of 7 50x10 m s Through what potential difference must the electron pass to accomplish this Vinitial Viinal Submit VAE 4 Part B Previous Answers Request Answer X Incorrect Try Again 9 attempts remaining V Thmunh what potential difference must the electron pass if it is to be slowed from 7 50x10 m s to a halt

Work function of two m surfaces are 2 0 eV and 3 0 eV Both are illuminated by light energy of incident photons greater than 3 eV If graph is plotted between maximum kinetic energy and frequency for both surfaces then slope of the graphs are in the ratio Only one correct answer A 2 3

A luminious object is placed 20 cm from surface of a convex mirror and a plane mirror is set so that virtual images formed in two mirror coincide If plane mirror is at a distance of 12 cm from object then focal length of convex mirror is 1 5 cm 2 10 cm

Given wave function for an electron magnetic wave to be y x t 10 sin 3 106 x 9 x 1014 t The speed of wave is Question Type Single Correct Type 1 2 108 m s 2 108 m s 3 3 108 m s x

Q16 From NCERT The photon radiated from hydrogen corresponding to the second line of Lyman series is absorbed by a hydrogen like atom X in the second excited state As a result the hydrogen like atom X makes a transition to nth orbit Then 1 X Het n 4 2 X Litt n 6 3 X Het n 9 4 X Li n 9

50 From NCERT NEET 2016 A black body is at a temperature of 5760 K The energy of radiation emitted by the body at wavelength 250 nm is U at wavelength 500nm is U and that at 1000nm is U3 Given Wien s constant b 2 88 x 106 nm K Which of the following is correct 1 U3 0 2 U1 U 3 U U 4 U 0

The graph shown below shows variation of de Broglie 1 wavelength A versus where Vis accelerating potential for three charged particles of equal charges but different masses 2 B O MA MB mc MB mc mA MA mc mB A 1 V

Identify the correct relation for the given diagram for frequency K V03 V02 V01 V1 V2 V3 V2 V3 V1 V3 V2 V1 V1 V2 V3 O anode potential

Figure shows the anode potential vs photo current graph when photons of 6 eV are incident on cathode in a photoelectric In set up the same set up if photons of 8 eV and same intensity are incident on cathode then anode potential vs photo current graph will be assume 100 efficiency of photons to eject photo electrons in both cases experiment experimental photocurrent t 3V 0 anode potential Question Type Single Correct Type i l

A photon of energy 4 eV is incident on a metal surface whose work function is 2 eV The minimum reverse potential to be applied for stopping the emission of electrons is 2 4V 4 8V 2V 3 6V TI

A particle P is formed due to a completely inelastic collision of particles x and y having de Broglie wavelengths y and respectively If x and y were moving in opposite directions then the de Broglie wavelength of P is 9 Apr 2019 I a Y Y b YxYV Y Yy X KY