ZIET BHUBANESWAR

Chapter–11: Dual Nature of Radiation and Matter

MULTIPLE CHOICE QUESTIONS

S.NO. QUESTIONS
1 Photoelectric effect reveals the:
(a) wave nature of radiation
(b) particle nature of radiation
(c) both wave and particle aspect of radiation
(d) electromagnetic nature of radiation
2 Photoelectric emission occurs only when the incident light has more than a certain minimum:
(a) frequency
(b) power
(c) wavelength
(d) intensity
3 The momentum of a photon of energy 1 MeV in kg m/s will be:
(a) 5 x 10-22
(b) 0.33 x 106
(c) 7 × 10-24
(d) 10-22
4 If λ stands for mid-wavelength in the visible region, the de Broglie wavelength for 100 V
electrons is nearest to :
(a) λ/5
(b) λ/50
(c) λ/500
(d) λ/5000
5 The momentum of a photon of an electromagnetic radiation is 3.3 × 10-29 kg m/s. What is the
frequency of the associated waves? [h=6.6x 10-34 Js; c=3x 108 m/s]
(a) 1.5x 10¹3 Hz
(b) 7.5 x 10¹2 Hz
(c) 6 × 10³ Hz
(d) 3 x 10³ Hz
6 The wavelength of a 1 keV photon is 1.24x 10-9 m. What is the frequency of 1 MeV photon?
(a) 1.24 x 10¹5 Hz
(b) 1.24 x 10¹8 Hz
(c) 2.4 x 1020 Hz
(d) 2.4 x 1023 Hz
7 The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected
photoelectrons was found to be 1.68 eV. The work function of the metal is:
(a) 3.09 eV
(b) 1.51 eV
(c) 1.42 eV
(d) 1.68 eV
(hc=1240 eV nm)
8 A photocell is illuminated by a source of light, which is placed at a distance ‘d’ from the cell. If
the distance becomes d/2, then number of electrons emitted per second will be:
(a) same
(b) four times
(c) two times
(d) one-fourth
9 By photoelectric effect, Einstein proved:
(a) E = hv
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 (b) KE= ½ mv2
(c) E = mc²
(d) KE = -Rhc2/n2
10 When UV rays are incident on a metal plate, photo-electric effect does not occur. It occurs by
incidence of :
(a) infrared
(b) X-rays
(c) radio wave
(d) microwave
11 In a photoelectric experiment, anode potential is plotted against plate current

(a) A and B will have same intensities while B and C will have different frequencies
(b) B and C will have different intensities while A and B will have different frequencies
(c) A and B will have different intensities while B and C will have equal frequencies
(d) B and C will have equal intensities while A and B will have same frequencies
12 Which of the following figures represents the variation of particle momentum with associated de
Broglie wavelength?

13 The correct graph representing the relation between energy (E) of photoelectrons and frequency
(ν) of incident light is

14 Shining light of wavelength λ and intensity I on a surface S produces photoelectrons at rate R and
with maximum kinetic energy E. Consider the following statements for the effect of changing one
parameter at a time :

(i) doubling I always doubles R

(ii) doubling I does not change E at all
(iii) making half always makes E more than 2 fold.
The statements true are:
(a) (i) and (ii) only
(b) (i) and (iii) only
(c) (ii) and (iii) only
(d) all the three
15 The energy that should be added to an electron to reduce its de Broglie wavelength from 1 nm to
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 0.5 nm is :
(a) four times the initial energy
(b) equal to its initial energy
(c) twice the initial energy
(d) thrice the initial energy
16 The emission of electron from a surface is possible due to
(a) Photoelectric effect
(b) Thermo ionic effect
(c) Both (a) and (b)
(d) None of the above
17 The magnitude of photoelectric current depends upon:
(a) frequency
(b) Intensity
(c) Work function
(d) Stopping potential
18 A photon of energy 4 eV incident on a metal surface having work function 2 eV , the minimum
reverse potential to be applied to stop the emission of electron will be
(a) 8 V
(b) 6 V
(c) 4 V
(d) 2 V
19 Lights of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively
successfully illuminates a metal surface whose work function is 0.5 eV, the ratio of maximum
kinetic energies will be :
(a) 1:2
(b) 2:1
(c) 1:4
(d) 4:1
20 For photoelectric emission ,tungsten requires light of 2500 A0 , if light of wavelength 2000 A0 is
incident , then emission will
(a) Takes place
(b) does not takes place
(c) Can’t say
(d) Depends on frequency
21 In a Photoelectric experiment the wavelength of incident radiation decreases, then
(a) Stopping potential will decrease
(b) Stopping potential will increase
(c) Maximum kinetic energy of emitted electrons will decrease

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 (d) Work function will decrease
22 When photons of energy h√ falls on a metal plate of work function W0 , photoelectrons of
maximum kinetic energy K are ejected , if the frequency is now doubled , the maximum kinetic
energy of the ejected photoelectrons will be
(a) K
(b) 2K
(c) K + W0
(d) K + h√
23

Figure shows variation of stopping potential (V0) vs. frequency (ν) of incident radiation for two
metals X and Y. Which metal will emit electrons of larger kinetic energy for same wavelength of
incident radiation?
(a) metal X
(b) metal Y
(c) Both will have same kinetic energy
(d) Can’t say from the graph
24 The slope of frequency of incident light and stopping potential for a given photosensitive surface
will be
(a) h
(b) h/e
(c) eh
(d) e
25 The De-Broglie wavelength associated with a tennis ball of mass 60 gram moving with a velocity
10 m/sec will be (h= 6.6 x 10-34 Js)
(a) 10-16 m
(b) 10-25 m
(c) 10-33 m
(d) 10-34 m
26 Following figure shows a plot of the de-Broglie wavelength ‘λ’ vs. ,. in case of two particles

having the same charge ‘q’ but different masses m1 and m2 (where V is the accelerating

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 potential), Which line A or B represents the particle of greater mass?

(a) A and B will have same mass

(b) Line B represent greater mass
(c) Line A represent greater mass
(d) can’t be determined from the data.
27 The graph below shows the variation of Photoelectric current with anode potential, which of the
following statement is wrong?

(a) Stopping potential does not depend upon the frequency.

(b) Saturation current does not depend upon the frequency
(c) Intensity of light for all the three radiations are equal
(d) Kinetic energy increases as stopping potential increases
28 The slope of stopping potential versus frequency of incident radiation is found to be 4.14 X 10-15
Vs in an experiment of photoelectric effect. Find the value of Plank’s constant.

(a) h= 6.624 x 10-34 Js

(b) h= 6.6 x 10-36 Js
(c) h= 6.6 x 10-30 Js

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 (d) h= 13.2 x 10-34 Js
29 Work function of Aluminium is 4.2 eV , if two photons each of energy 3.5 eV strike an electron
of Aluminium simultaneously ,then emission of electron will
(a) One photon is sufficient.
(b) possible
(c) not possible
(d) Data incomplete
30 Light of wavelength 5000 A0 is incident on photosensitive surface whose work function is 1.9 eV.
Find the stopping potential.
(a) 0.58 volt
(b) 0.58 eV
(c) 5.8 volt
(d) 5.8 Ev
31 Minimum energy required by an electron to just escape from the metal surface so as to overcome the
restraining forces at the surface is known as
(A) Photoelectric emission
(B) work function
(C) free electrons
(D) all of these

32 The theory, on the basis of photoelectric effect can be explained:

(A) Corpuscular theory
(B) Electromagnetic theory
(C) Wave theory
(D) Quantum theory

33 Which of the following has maximum stopping potential when metal is illuminated by visible light?
(A) Red
(B) Yellow
(C) Blue
(D) Violet

34 The slop of frequency of incident ray and stopping potential for a given surface will be
(A) h
(B) e
(C) eh

(D)

35 When radiation of given frequency is incident upon different metals, the maximum kinetic energy of

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 electrons emitted
(A) increase with increase of work function
(B) decrease with increase of work function
(C) does not depend upon work function
(D) remains same with the increase of work function

36 If the work function of a metal is ‘ ’ and the frequency of the incident light is ‘ ’, there is no emission of
photoelectron if

(A)

(B)

(C)

(D)

37 Light of frequency 1.5 times the threshold frequency is incident on photosensitive material. If frequency is
halved and intensity doubled, then the photocurrent is
(A) zero
(B) quadrupled
(C) halved
(D) doubled

38 Light of wavelength ‘λ’ strikes a photosensitive surface and electrons are ejected with kinetic energy ‘E’.
If the kinetic energy is to be increased to ‘2E’, the wavelength must be changed to

(A)

(B) 2λ

(C) greater than

(D) greater than 2λ

39 The maximum kinetic energy of emitted photoelectrons against frequency of incident radiation is
plotted as shown in figure. The slop of the graph is equal to

(A) charge on electron

(B) work function of emitter
(C) Plank’s constant
(D) ratio of Plank’s constant and charge on electron

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40 Two particles have equal momentum. What is the ratio of their de-Broglie wavelength?
(A) 0.5
(B) 1
(C) 2
(D) 3

41 Which of the following statement is not correct?

(A) Photographic plates are sensitive to infra-red rays.
(B) Photographic plates are sensitive to ultraviolet rays.
(C) Infra-red rays are visible but can cast shadows like visible light.
(D) Infra-red photons have more energy than photons of visible light.

42 The work function of metal is 1 eV. Light of wavelength 3000 is incident on this metal surface. The
velocity of emitted photoelectrons will be
(A) 10 m/s
(B) 1x103 m/s
(C) 1x104 m/s
(D) 1x106 m/s

43 Energy from the sun is received on earth at the rate of 2 cal per cm2 per min. If average wavelength of
solar light be taken at 5500 A0 then how many photons are received on the earth per cm2 per min?
(A) 1.5 x 1013
(B) 1.75 x 1019
(C) 2.3 x 1019
(D) 2.9 x 1013

44 The momentum of a photon is 3.3 x 10-29 kg ms-1. Its frequency will be

(A) 1.5x1013 Hz
(B) 7.5x1012 Hz
(C) 6x103 Hz
(D) 3x103 Hz

45 Photocells are NOT used in

(A) exposure meter
(B) operating relay system
(C) induction furnace
(D) reproduction of sound in films

46 A particle of mass M at rest decay in to two particles of masses m1 and m2 having non zero
velocities. The ratio of the de-Broglie wavelength of the particles λ1/ λ2 is:
(A) m1/ m2

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 (B) m2/ m1
(C) 1.0
(D) √m2 /√m1
47 In photoelectric effect, electrons are ejected from metals if the incident light has a certain
minimum:
(A) Wavelength
(B)Frequency
(C)Amplitude
(D)Angle of incidence

48 If following particles are moving with same velocity then which has maximum de-Broglie wavelength? :

(A) Proton

(B)α-particle

(C)Neutron

(D)β-particle

49 As the intensity of incident light increases :

(A) Photoelectric current increases

(B) Kinetic energy of emitted photoelectrons increases

(C) Photoelectric current decreases

(D) Kinetic energy of emitted photoelectrons decreases

50 Which of these particles (having the same kinetic energy) has the largest de-Broglie wavelength? :

(A) Electron

(B)Alpha particle

(C)Proton

(D)Neutron

51 De-Broglie wavelength λ associated with neutron is related with absolute temperature T is :

(A) λ α T
(B) λ α 1/T

(C) λ α 1 /√

(D) λ α √
52 If the kinetic energy of a free electron doubles its de-Broglie wavelength changes by the factor:

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 (A) ½
(B)2
(C) 1/√2
(D) √2

53 The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall
on it is 4 eV. The stopping potential, in volt is :

(A) 2
(B)4
(C)6
(D)10

54 The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with
1 MeV energy is nearly :
(A) 1.2 nm
(B) 1.2 × 10–3 nm
(C) 1.2 × 10–6 nm
(D) 1.2 × 10 nm

55 Consider a beam of electrons (each electron with energy E0) incident on a metal surface kept in an
evacuated chamber. Then :
(A) no electrons will be emitted as only photons can emit electrons.
(B) electrons can be emitted but all with an energy, E0.
(C) electrons can be emitted with any energy, with a maximum
of E0– f (f is the work function).
(D) electron can be omitted with energy, with a maximum of E0.

56 Kinetic energy of electrons emitted in photoelectric effect is:

(A) directly proportional to the intensity of incident light.
(B) inversely proportional to the intensity of incident line.
(C) independent of the intensity of incident light.
(D) independent of the frequency of light.

57 Threshold wavelength of a photoelectric emission rom a material is 600 nm. Which of the following
illuminating source will emit photoelectrons? :
(A) 400 W, infrared lamp
(B) 10 W, ultraviolet lamp
(C) 100 W, ultraviolet lamp
(D) Both (B) & (C)

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58 At stopping potential, the kinetic energy of emitted photoelectron is:
(A) minimum.
(B) maximum.
(C) zero.
(D) cannot de-predicted

59 The ratio of de-Broglie wavelength associated with two electrons accelerated through 25 V and 36 V is :
(A) 25/36
(B) 36/25
(C) 5/6
(D) 6/5

60 Kinetic energy of electrons emitted in photoelectric effect is:

(A) directly proportional to the intensity of incident light.
(B) inversely proportional to the intensity of incident light.
(C) independent of the intensity of incident light.
(D) independent of the frequency of light.

61 Name the scientist who was the first to determine experimentally the speed and the specific charge of the
cathode way particle-

Maxewell
J.J Thomsan
Roingten
Hertz
62 Which experiment established that charge is quantized-

Hertz Experiment
Davission and Germer experiment
Milllikan’s experiment
None of these
63 For a given frequency of the incident radiation ,the stopping potential :

Increases with intensity

Decreases with intensity
Independent of intensity
None of these
64 The minimum energy required to eject an electron from the surface of metal surface is called

(A) Kinetic energy

(B) Potential energy
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 (C) Work function
(D) None of these
65 An electron, an alpha and a proton have the same kinetic energy. Which of these particle has the shortest
de Broglie wavelength;

( A) Electron

( B) Proton

(C) Alpha particle

(D) All of these

66 The de – Broglie wavelength associated with an electron accelerated through a potential difference of 100
volts:

( A) 0.123 nm

( B ) 0.534 nm

( C) 0.234nm

( D) 0.233nm

67 The work function of photoelectric material is 3.3 eV. The threshold frequency will be equal to:
( A) 8 × 1014 Hz
( B) 8 × 1010 Hz
( C) 5 × 1010 Hz
( D) 4 × 1014 Hz

68 The momentum of an electron that emits a wavelength of 2 Å. will be:

( A) 6.4 × 10-36 kgms-1
(B) 3.3 × 10-24 kgms-1
(C) 3.3 × 10-34 kgms-1
(D) none of these

69 The frequency and the intensity of a beam of light falling on the surface of photoelectric material are
increased by a factor of two. This will:
( A) increase the maximum K.E. of photo-electron as well as photoelectric current by a factor of two.

(B) increase maximum K.E. of photoelectrons and would increase the photo current by a factor of two.
( C) increase the maximum K.E. of photo electrons by a factor of two and will no affect photoelectric
current.
( D) No effect on both maximum K.E. and photoelectric current.

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70 According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo
electrons from a metal vs the frequency, of the incident radiation gives a straight line whose slope :

(A) depends on the nature of the metal used

(B) depends on the intensity of the radiation

(C) depends both on the intensity of the radiation and the metal used

(D) is the same for all metals and independent of the intensity of the radiation.

71 The ratio of specific charge of an alpha particle to the proton is:

(A) 1 : 2
(B) 2 : 1
(C) 4 : 1
(D) 1 : 4

72 When a yellow light is incident on a surface, no electrons are emitted while green light can emit electrons.
If the red light is incident on the surface then:
(A) no electrons are emitted
(B) photons are emitted
(C) electrons of higher energy are emitted
(D) electrons of lower energy are emitted

73 In photoelectric effect, electrons are ejected from metals, if the incident light has a certain minimum

Wavelength
Frequency
Amplitude
Angle of incidence
74 The wavelength of photon is proportional to
(E) Frequency
(F) √frequency
(G) 1/√frequency
(H) 1/frequency
75 What is energy of a photon whose wavelength is 6840 Å?
(a) 1.81 eV
(b) 3.6 eV
(c) -13. 6 eV
(d) 12.1 eV

76 Particle nature and wave nature of electromagnetic waves and electrons can be shown by
(a) Electrons have small mass, deflected bi metal sheet
(b) X rays are diffracted, reflected by thick metal sheet
(c) Light is reflected and diffracted
(d) Photo electricity and electron microscope
77 Electron volt is unit of

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 (a) Energy
(b) Potential
(c) Current
(d) Charge
78 De-Broglie wavelength of a body of mass m and kinetic energy E is given by (symbols have their
usual meanings):
h/√2mE
h/2mE
2m/√Eh
h/mE
79 The de-Broglie wavelength of an electron moving with a speed of 6.6 × 1015 ms-1 is nearly equal to
(a) 10-11m
(b) 10-9 m
(c) 10-7 m
80(d) 10-5 m

80 An electron accelerated through a potential difference of V volt has a wavelength λ associated

with it, Mass of proton is nearly 2000 times that of an electron. In order to have the same λ for
proton, it must be accelerated through a potential difference (in volt) of
(a) V
(b) √2000 V
(c) 2000/√ V
(d) V/2000
81 The energy E and momentum p of a photon is given by E = hv h and p = hλ. The velocity of photon will
be
(a) E/P
(b) (E/P)²
(c) √E/P
(d) (EP)2

82 Ultra-violet radiation of 6.2 eV falls on an aluminium surface having work-function 4.2 eV. The kinetic
energy (in J) of the fastest electron emitted is nearly.

3 × 10-19
3 × 10-15
3 × 10-17
3 × 10-21
83 The threshold frequency for a certain metal is v0. When light of frequency v = 2v0 is incident on it, the
maximum velocity of photo electrons is 4 × 106ms-1. If the frequency of incident radiation is increased to 5
v0, then the maximum velocity of photo electrons (m/s) is
(a) 8 × 105
(b) 2 × 106
(c) 2 × 107
(d) 8 × 106

84 Which of the following is not the property of photons

charge
rest mass
energy
momentum
85 Dynamic mass of photon of wavelength k is
(a) Zero
(b) hc/λ
(c) h/cλ
(d) h/2 λ
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86 When light is directed at the metal surface, the emitted electrons:
(a) are called photons
(b) have energies that depend upon the intensity of light.
(c) have random energies.
(d) have energies that depend upon the frequency of light

87 The momentum of an electron that emits a wavelength of 2 Å. will be:

(a) 6.4 × 10-36 kgms-1
(b) 3.3 × 10-24 kgms-1
(c) 3.3 × 10-34 kgms-1
(d) none of these
88 The process of pilling out of electrons form metal by applying strong electric field (in order of
is called

(A) Thermionic emission

(B) Field emission

(C) Photoelectric emission.

(D) Radioactive emission

89 Wave theory cannot explain photoelectric effect because in photoelectric effect, it is observed that

(A) for the frequency of light below a certain value, the photoelectric effect does not take place, whatever
be the frequency.

(B) maximum kinetic energy of emitted electrons is independent of intensity of radiation.

–
(C) the photoelectric emission is an instantaneous process without any apparent time lag (~ or less),
even when the incident radiation is made exceedingly dim.

(D) all of these

90 The work-function of a metal is defined as

(A) the maximum potential difference provided to the metal to pull out electrons.

(B) the minimum potential difference provided to the metal to pull out electrons.

(C) the maximum energy needed by an electron to come out from a metal.

(D) the minimum energy needed by an electron to come out from a metal.

91 Which of the following colour will have maximum stopping potential when visible light is incident on a
metal surface?

(A) Blue

(B) Violet

(C) Red

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 (D) yellow

92 Photons are deflected by

(A) electric field only

(B) magnetic field only

(C) both electric and magnetic field

(D) none of the above

93 A photon does not have

(A) rest mass

(B) frequency

(C) momentum

(D) energy

94 The threshold wavelength for a metal having work function φ0 is λ what will be the threshold wavelength
for a metal whose work function is φ0 / 2.

(A) λ

(B)

(C)

(D)

95 If the following figure shows the variation of photoelectric current with collector plate potential for
different frequencies of incident radiation, then

(A) ν

(B) ν

(C) ν

(D) ν

96 The variation of stopping potential with frequency ν of incident radiation for a given photosensitive

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 material is shown below, the Plank’s constant will be equal to

(A) the slope of the graph.

(B) the product of slope of the graph and charge on the electron.

(C) the product of Y-intercept of the graph and charge on the electron.

(D) the product of slope of the graph and mass of the electron.

97 If we consider electrons and photons of same wavelength, then they will have same

(A) momentum

(B) velocity

(C) energy

(D) speed

98 If uncertainty in the position of an electron is zero the uncertainty in its momentum will be

(A)

(B)

(C) zero (0)

(D) infinite (

99 To reduce de-Broglie wavelength of an electron from then its energy should be

(A) increased to 3 times

(B) decreased to 1/3 times

(C) increase to 9 times

(D) decreased to 1/9 times

100 For same energy (E), what will be the ratio of (given ‘m’ is mass of electron)

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 (A)

(B)

(C)

(D)

101 The photoelectric work function for a metal surface is 4.14 ev. The cutoff wavelength for this is

(a) 4125 Å (b) 2062.5 Å (c) 3000 Å (d) 6000 Å

102 If E1,E2,E3,E4 are the respective kinetic energies of electron, deuteron, proton and neutron having same
De- Broglie wavelength. Select the correct order in which those values would increase

a) E1,E3,E4,E2 b) E2,E4,E1,E3 c)E2,E4,E3,E1 d)E3,E1,E2,E4

103 When radiation of given frequency is incident upon different metals, the maximum kinetic

energy of electrons emitted

(a) decrease with increase of work function

(b) increase with increase of work function

(c) remains same with the increase of work function

(d) does not depend upon work function

104 A proton, a neutron, an electron and alpha particle have same kinetic energy, then their DeBroglie
wavelengths compare as

a. λe = λp= λn = λa
b. λe>λp>λn>λa
c. λa<λp<λn<λe
d. λp = λn & λe>λa
105 Following graph shows the variation of photoelectric current with anode potential for two light beam of
same wavelength but different intensity. Find the correct relation :

e. I1> I2 b. I1=I2 c.I1<I2 d. I1≤I2

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106 The slope of frequency of incident ray and stopping potential for a given surface will be
(a) h (b) h/e (c) eh (d) e

107 The threshold wavelength for a metal having work function ϕ0 is λ0 , what is the threshold wavelength for
a metal whose work function is ϕ0 /2 .

(a) 4 λ0 (b) 2 λ0 (c) λ0 /2 (d) λ0 /4

108 Maximum kinetic energy of emitted electron depends on the frequency of incident photon when frequency
of incident photons is

f. equal to the threshold frequency

g. half of threshold frequency
h. greater then threshold frequency
i. one third of threshold frequency
109 Two particles have equal momentum. What is the ratio of their de-Broglie wavelength?

(a) 2 (b) 1 (c) 3 (d) 0.5

110 Which of the following has maximum stopping potential when metal is illuminated by visible light?

(a) Blue (b) Yellow

(c) Violet (d) Red

111 The wavelength of matter waves is independent of

(a) Mass (b) Velocity (c) Momentum (d) Charge

112 A proton and an alpha particle are accelerated through the same potential difference. The ratio of de
Broglie wavelength of the proton to that of the alpha particle will be

(a) 2 : 1 (b) 1 : 1 (c) 1 : 2 (d) 2√2 : 1

113 If in a photoelectric cell, the wavelength of incident light is changed from 4000 Å to 3000 Å then change
in stopping potential will be

(a) 0.66 V (b) 1.03 V (c) 0.33 V (d) 0.49 V

114 Kinetic energy of emitted electrons depends upon:

(a) Frequency (b) intensity
(c) Nature of atmosphere surrounding the electrons (d) none of these

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115 The ratio of specific charge of an alpha particle to the proton is:
(a) 1 : 2 (b) 2 : 1 (c) 4 : 1 (d) 1 : 4
116 The work function of photoelectric material is 3.3 eV. The threshold frequency will be equal to:
(a) 8 × 1014 Hz (b) 8 × 1010 Hz (c) 5 × 1010 Hz (d) 4 × 1014 Hz
117 The strength of photoelectric current depends upon:
(a) Angle of incident radiation (b) frequency of incident radiation
(c) Intensity of incident radiation (d) distance between anode and cathode
118 Which of the following radiations cannot eject photo electrons?
(a) Ultraviolet (b) Infrared (c) Visible (d) X-rays
119 What is the de-Broglie wavelength of an electron accelerated from rest through a potential
difference of 100 volts?
(a) 12.3 Å (b) 1.23 Å (c) 0.123 Å (d) None of these
120 When a yellow light is incident on a surface, no electrons are emitted while green light can emit
electrons. If the red light is incident on the surface then:
(a) No electrons are emitted (b) photons are emitted
(c) Electrons of higher energy are emitted (d) electrons of lower energy are emitted
121 8. Evidence of the wave nature of light cannot be obtained from:
(a) diffraction (b) interference (c) doppler effect (d)
reflection
122 9. When an electron jumps across a potential difference of 1 V, it gains energy equal to:
(a) 1.602 × 10-19 J (b) 1.602 × 1019 J (c) 1.602 × 1024 J
(d) 1 J
123 10. Protons and alpha particles have the same de-Broglie wavelength. What is same for both of
them?
(a) Energy (b) Time period (c) Frequency (d) Momentum
124 The theory, on the basis of photoelectric effect can be explained:

(a) Corpuscular theory

(b) wave theory

(c) electromagnetic theory

(d) Quantum Theory

125 Identify the correct relation for the given diagram for frequency

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 (a) v1 = v2 = v3

(b) v1 > v2> v3

(c) v1 < v2< v3

(d) v1 =2 v2 = 3v3

126 Light of frequency 1.9 times the threshold frequency is incident on a photosensitive material. If the
frequency is halved and intensity is doubled, the photo current becomes:

(a) doubled

(b) quadrupled

(c) halved

(d) zero

127 Radiation of frequency ν is incident on a photosensitive metal. When the frequency of the incident
radiation is doubled, what is the maximum kinetic energy of the photoelectrons?

(a)4E
(b)2E
(c)E + hν
(d)E – hν
PREPARED BY :
PGTs OF BHUBANESWAR, GUWAHATI,KOLKOTA ,RANCHI,SILCHAR,TINSUKIA regions.
VETTED BY :SILCHAR REGION

1.KEY/ANSWER SHEET

Q.No. ANSWER

Q.No.1 (b)

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Q.No.2 (a) KE = h(ν-ν0), for photoelectron emission, ν ≥ ν0

Q.No.3 (a) p = E/c = 1.6 x 10-13 J/ 3 x 108 m/s = 5 x 10-22 kg m/s

Q.No.4
(d) de Broglie wavelength λB = 12.27/ Å = 1.227 Å = λ/ 5000,
where λ is mid wavelength in the visible region= 6000 Å

Q.No.5 (a) p = E/c = hν/c so, ν = pc/h = 3.3 x 10-29 x 3 x 108/ 6.6 x 10-34 = 1.5 x 1013 Hz

Q.No.6 (c) E1/E2 = hν1/ hν2 = ν1/ ν2

so, ν2 = (E2/E1) ν1 = (E2/E1) (c/λ1) = 2.4 x 1020 Hz

Q.No.7 (c) hν = hc/λ = 1240 eV nm/400 nm = 3.1 eV

ϕ0 = hν – K = 3.1 eV – 1.68 eV = 1.42 eV

Q.No.8 (b) Number of photon (N) ∝ intensity of light ∝ 1/d2. When d becomes d/2, N becomes 4N

Q.No.9 (a)

Q.No.10 (b) X-rays have greater frequency than UV rays.

Q.No.11 (d) B and C have equal intensities as they have equal saturation currents. A and B have same stopping
potential and as such have same frequencies.

Q.No.12 (d) de-Broglie wavelength, λ = h/p

Q.No.13 (c) K = h (ν-ν0)

Q.No.14 (d)

Q.No.15 (d)

16 (c) Both (a) and (b)

17 (b) Intensity

18 (d) 2 V

19 (c) 1:4

20 (a) Takes place

21 (b) Stopping potential will increase

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22 (d) K + h√

23 (a) metal X

24 (b) h/e

25 (c) 10-33 m

26+ (c) Line A represent greater mass

27 (a) Stopping potential does not depend upon the frequency.

28 (a) h= 6.624 x 10-34 Js

29 (c) not possible

30 (a) 0.58 volt

31 B

32 D

33 D

34 D

3 B

36 A

37 A

38 C

39 C

40 B

41 D

42 D

43 C

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44 A

45 C

46 C- 1.0

47 B- Amplitude

48 D - β-particle

49 A - Photoelectric current increases

50 A – Electron

51 C - λ α 1 /√

52 C -1/√2

53 B–4

54 B - 1.2 × 10–3 nm

55 D- electron can be emitted with energy, with a maximum of E0.

56 C - independent of the intensity of incident light.

57 D - Both (B) & (C)

58 C - zero.

59 C - 5/6

60 C - independent of the intensity of incident light.

61 B 73 b

62 C 74 d

63 C 75 a

64 C 76 d

65 C 77 a

66 A 78 a

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67 A 79 b

68 C 80 d

69 B 81 a

70 D 82 a

71 A 83 d

72 A 84 a and b

85 c

86 d

87 b

88 (B) Field emission

89 (D) all of these

90 (D) the minimum energy needed by an electron to come out from a metal.

91 (B) Violet

92 (D) none of the above

93 (A) rest mass

94 (B)

95 (C)ν1

96 (B) the product of slope of the graph and charge on the electron.

97 (A) momentum

98 (D) infinite (

99 (C) increase to 9 times

100
(A)

101 C) 3000 Å

102 C) E2,E4,E3,E1

103 A) decrease with increase of work function

104 B) λe > λp > λn > λa

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105 C) I1 < I2

106 B) h/e

107 B) 2 λ0

108 C) greater then threshold frequency

109 B) 1

110 C) violet

111 D) charge

112 D) 2√2 : 1

113 B) 1.03 V

114 (a) Frequency

115 (a) 1 : 2

116 (a) 8 × 1014 Hz

117 (c) Intensity of incident radiation

118 (c) Visible

119 (b) 1.23 Å

120 (a) No electrons are emitted

121 (d) reflection

122 (a) 1.602 × 10-19 J

123 (d) Momentum

124 3. (d) Quantum Theory

125 (b) v1 > v2> v3

126 (d) zero

127 (c)E + hν

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