Photoelectric Effect Questions and Answers

1 1 In the experiment of photon kmax is Ko If frequency is increased by factor n then kax is nako Find work function max 1 2 K n 3 n n Ko 2 4 n n n n n n K K

In Millikan s oil drop experiment an oil drop of mass 16 10 6 kg is balanced by an electric field of 106 Vm The charge in coulomb on the drop is assuming gap g 10ms 2 A B C D 6 2x10 11 16x10 9 16 10 11 16 10 13

19 A particle X of mass m and initial velocity u collide with another particle Y of mass which is at rest The 3m 4 collision is head on and perfectly elastic The ratio of de Broglie wavelengths y and x after the collision is lo a 4 3 d 3 32 b 2 32 c 3 4

Photoelectric effect experiments are performed using two different plates of silver and sodium having work functions 4 6 eV and 2 3 eV respectively A light beam of wavelength 200 nn illuminates each plates Then Take hc 1240 eV nm A Ratio of maximum kinetic energy of ejected photoelectrons is 0 41 B Ratio of threshold frequency is 0 5 C Ratio of threshold wavelength is 0 5 D Batio of slope of the stonning potential versus frequency plot is 1

A parallel beam of radiation is incident on a highly conducting sphere of unknown emissivity The intensity of incident radiation on sphere is 912 W m Take stefan Boltzman constant o 5 7 x 10 Wm 2k4 and sorrounding temperature is 300 K Assume that the energy exchange with sorrounding is only through radiation Find the final steady state temperature of the body in C Take 11 3 32 and 7 2 65 O Incident radiations

If frequency of incident light is constant then choose the correct option Photo current Maximum kinetic energy O Maximum kinetic energy Intensity Intensity Both 1 2 Intensity

33 Photons of energy 7 eV are incident on two metals A and B with work functions 6 eV and 3 eV respectively The minimum de Broglie wavelengths of the emitted photoelectrons with maximum energies are A and AB respectively where A AB is nearly

In Millikan s oil drop experiment an oil drop of radius r and charge Q is held in equilibrium between the plates of a charged parallel plate capacitor when the potential difference is V To keep a drop of radius 2r and charge 2Q in equilibrium between the plates the potential difference required will be

C 2 d 4 44 When photons of energy hy fall on an aluminum plate of work function E photoelectrons of maximum kinetic energy K are ejected If the frequency of the radiation is doubled the maximum kinetic energy of the ejected photoelectrons will be 2006 a K E b 2K c K d K hy

Two particles A and B of de Broglie wavelength X and AB are in motion in one dimension They combine to form a particle C This process conserves momentum The incorrect relation of de Broglie wavelength of Cin relation to that of A and B is Onc Oc Onc ONC AXB 2A 2B AX B B A AX B 2 23 AX B 2

Which one of the following is true in photoelectric emission A Photoelectric current is directly proportional to the amplitude of light of a given frequency Photoelectric current is directly proportional to the B intensity of light of a given frequency above threshold value Above the threshold frequency the maximum K E C of photoelectrons is inversely proportional to the frequency of incident light D The threshold frequency depends upon the wavelength of incident light

Does not depend on the frequency of the incident light Does not depend on nature of cathode material O Depends on both the frequency of incident light and nature of cathode material O Depends upon the intensity of incident light

Question 32 When monochromatic light of intensity I and frequency v 3vo Vo is the threshold frequency is incident on the cathode in a photoelectric experiment setup the saturation current is 0 found to be 24 and the stopping potential is Vo The photoelectric efficiency of the photo metal used to coat the cathode is independent of the frequency of incident radiation If the Intensity of the incident radiation is doubled and its frequency halved then choose the correct statement s Cathode H Options Vo a The stopping potential is 2 Vo 2 b The stopping potential is c The saturation photo current is 4 A d The saturation photo current is 8 A HIT

158 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 a 2 8 10 m X 28 x 10 12 2015 RS b 2 8 10 m 28 10 10 16

Two particles A and B of de Broglie wavelength X and ar in motion in one dimension They combine to form a particle C This process conserves momentum The incorrect relation of de Broglie wavelength of C in relation to that of A and B is c O NO O no AX B 2A 2B AX B B A AX B 2 AX B

3 2 10 C 4 2 x 10 C 23 When a high energy UV photon beam enters an electric field it will be 24 1 accelerated 3 undeflected Two waves represented by v 2 retarded 4 none of these 10 sin 2000m 2x

The ionisation energies of K shell for cobalt copper and molebdenum are 7 8 9 0 and 20 1 keV respectively If any metal out of these is used as in an X ray tube operated at 15kV then target A The K series of characteristic X ray will be emitted by Co only B The K series of characteristic X rays will be emitted by Cu and Co only C The K series of characteristic X rays will be emitted by Cu Co and Mo D The minimum wavelength of continuous X rays emitted by the three metals will not be same 5

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 2011 a 1 8 V b 1 2V d 2 3 V c 0 5 V

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface having work function 5 01 eV when ultraviolet light of 200 nm falls on it must be 2010 a 2 4 V c 2 4 V b 1 2V d 1 2V

47 The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations Which one of the 2009 following is a correct statement photocurrent Retarding potential 1 Anode potential at Matter a Curves 1 and 2 represent incident 52 radiations of same frequency but of different intensities b Curves 2 and 3 represent incident radiations of different frequencies and different intensities c Curves 2 and 3 represent incident radiations of same frequency having same intensity d Curves 1 and 2 represent incident radiations of different frequencies and different intensities chromatic light of wavelength 667 nm is 53

73 A particular electromagnetic radiation with wavelength 200 nm a has a higher frequency than radiation with wavel 400 nm b is in the visible region of the electromagnetic spectrum c has a greater speed in vacuum than does radiation wavelength 400 nm d has a greater energy content per photon than doe radiation with wavelength 100 nm

A beam of light of wavelength 400 nm and power 1 55 mW is directed at the cathode of a photoelectric cell If only 10 of the incident photons effectively produce photoelectron then find current due to these electrons given hc 1240eV nm e 1 6 10 C

0 An electron of mass m and a photon have the same energy E in the range of a few eV The ratio of the de Broglie wavelength associated with the electron and the wavelength of the photon is c speed of light in vacuum 1 2 2m 4 1 2 E 2m 3 c 2mE 2 1 2E

2 By how much would the stopping potential for a given photosensitive surface go up if the frequency of the incident radiations were to be increased from 4 10 5 Hz to 8 10 5 Hz C and c 3 108 ms 10 15wod 20 Given h 6 4 x 10 34 J s e 1 6 x 10

For photoelectric effect in sodium the figure shows the plot of cut off voltage versus frequency of incident radiation Calculate i threshold frequency ii work function for sodium Cut off voltage in volts 0 1 2 3 4 5 6 7 8 9 10 x 10 4 Frequency in Hz

A parallel beam of monochromatic light of wavelength 6620 A striking a metal surface perpendicular has an intensity of 900 W m The number of photon striking the matal surface per unit area per second is O 3 x 1021 3 x 1019 4x1021 4x1019

Example 11 2 The work function of caesium is 2 14 eV Find the threshold frequency for caesium and the wavelength of the incident light if the photocurrent is brought to zero by a stopping potential of 0 60 V

41 Wave nature of light cannot explain photoelectric effect because in photoelectric effect it is seen that 1 For the frequency of light below a certain value the photoelectric effect does not take place irrespective of intensity 2 Maximum kinetic energy of ejected electrons is independent of intensity of radiation 3 There is no time lag between the incidence of radiation and emission of electrons 4 All of these

b Hydrogen atoms are excited with an electron beam of energy 12 5ev Find a the highest energy level up to which the hydrogen atoms will be excited c Find the ratio between the wavelength of the most energetic spectral lines in the Balmer and Paschen series of the hydrogen atom

In the given graph of the photoelectric experiment the maximum energy of emitted photoelectron will be 1 2 eV 2 0 eV 3 4 eV 443 144 3 2 1 0 wh 147 An is t the 1 2 3 4 148 In E of

mistry 10 Mathematic 30 English 5 Qs A beam of electromagnetic waves with a frequency of 6 28 x 10 15 Hz incident on a metal surface What is the maximum kinetic energy of the photoelectro emitted from the meta s surface if the work function of the metal is 4 0 eV Planck s constant 4 14 x 10 15eV s O A 22 eV O B 2 28 Ev O C 30 eV D 28 eV

1 When a metallic surface is illuminated with light of wavelength the stopping potential is V When the same surface is illuminated by light of wavelength 22 the stopping potential is The threshold V 3 wavelength for the surface is 42 3 b 42 c 62 a d B 3

1 Light in certain cases may be considered as a stream of particles called photons Each photon has a linear momentum h where h is the Planck s constant and is the wavelength of the light A beam of light of wavelength is incident on a plane mirror at an angle of incidence 0 Calculate the change in the linear momentum of a photon as the beam is reflected by the mirror

11 Let K be the maximum kinetic energy of photoelectrons emitted by light of wavelength 2 and K2 corresponding to wavelength 2 If A 2 2 then b K 2K d K 2K2 K2 4k a 2K K K c K 2

The retarding potential for having zero photo electric current 1 3 orrect Answer 4 ur Answer 3 aatus incorrect is proportional to the wavelength of incident light increases uniformaly with increase in wavelength of incident light is proportional to the frequency of incident light Increase uniformly with increase in frequency of incident light

Suppose a beam of electrons with each electron having energy E is incident on a metal surface kept in an evacuated chamber Then electrons can be emitted with any energy with maximum of E Correct Answer no electrons will be emitted as only photons of emit electrons no electrons can be emitted but all with an energy D electrons can be emitted with any energy will maximum of E being work function CHANNE

Exercise 13 2 Calculate the probability that in the example of Rutherford scattering just given an alpha particle is scattered through an angle greater than 10 2 radian in the laboratory frame Use the result to estimate the importance of multiple scattering in this example

An electron in the hydrogen atom jumps from excited state n to the ground state The wavelength so emitted illuminates a photosensitive material having work function 2 75 eV If the stopping potential of the photoelectron is 10 V the value of n is a 3 2011M c 5 b 4 d 2

Electrons emitted due to absorption of energy of radiation will have a maximum kinetic energy g is work function v is frequency of incident radiation 1 Kmas hu 2 Kmax hv 3 Kmax hu 4 Kmax hu

Intensity of light is 1 number of photons falling over an area in Is 2 number of photons falling over an area 3 number of photons falling over unit area in unit time 4 number of photons emitted by source in 1 s

Five elements A B C D and E have work functions 1 2 eV 24eV 3 6eV 4 8eV and 6eV respectively If light of wavelength 4000 A is allowed to fall on these elements then photoelectrons are emitted by O A B and C

The maximum wavelength of radiation that can produce photoelectric effect in certain metal is 200 nm The maximum kinetic energy acquired by electron due to radiation of wavelength 100 nm will be O 12 4 eV O 6 2 eV O 100 eV

3 The spectral emissive power E for a body at temperature T is plotted against the wavelength and area under the curve is found to be A At a different temperature T the area is found to be 625A Then 21 2 2 1 5 dE d 2 1 T T 2 1 5 3 1 5 4 5 20 21

Which of the following statements about photoelectric effect is are correct I When electron emission occurs the rate of emission of photoelectrons proportional to the intensity of is electromagnetic radiation incident on the metal II Electrons are emitted only when the incident electromagnetic radiation has a wavelength larger than some threshold value III Electrons are emitted only when the incident electromagnetic radition has an intensity greater than some threshold value A I only B II only C I and III only

The figure shows different graphs between stopping potential Vo and frequency v for photosensitive surface of cesium potassium sodium and lithium The plots are parallel Which of the following about their work function is correct V 1 Cesium i Potassium Sodium iv Lithium 5 0 5 2 5 4 5 6 5 8 1 i ii iii iv 2 i iii ii iv 3 iv iii ii i 4 i iii ii iv 10 Hz

Let the potential energy of a hydrogen atom in the ground state be zero Then its energy in the first excited state will be 1 10 2 eV 3 23 8 eV 2 13 6 eV 4 27 2 eV

Threshold wavelength of a metal surface is 5 10 7 m When it is illuminated by light of wavelength 3 x 10 7m stopping potential is Vo what will be stopping potential if wavelength of incident light is doubled Question Type Single Correct Type Vo

In a photoelectric effect experiment the stopping potential is 1 37 V if the light used to illuminate the cathode has wavelength 475 nm Find the work function in eV of the cathode material Express your answer in electron volts Submit Part F AEO Request Answer eV Find the stopping potential if the wavelength is decreased to 425 nm

Question Type Single Correct Type 1 Does not depend on the frequency of the incident light 2 Does not depend on nature of cathode material Depends on both the frequency of 3 incident light and nature of cathode material 4 Depends upon the intensity of incident

If the radiations of wavelength 3100 and 6200 are incident on a substance of work function 1eV one by one then the ratio of the stopping potentials for the emitted photoelectrons will be approx Question Type Single Correct Type 1 3 1 2 4 1 3 6 1