Unit - 17 Important Formula - Studiestoday

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Unit - 17Important Formula

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SUMMARY

1. Photon energy nhcE hf or E nhf

2. Number of photon emitted in one second EPN

3. Mamentum of Photon hc= p = mv =

4. Mass of Photon 2chfm

5. Work function 0

000hchfW

0

0

000

2maxmax hccchffhwhfmv

21K

OR

0 00

0 0

hceV hce

IAPAp

txAEI

TimeAreaEnergyIntensity

mk2pm2

pmv21KEnergyKinetic

22

6. De-Brogli wave length equation

2 3h h h hp mv mk mkT

1.23

2h nmmeV V

7. Braga's law for crlstal diffraction is 2d sin n

Thomsan Equation 2 21 2eVmv eV OR v ... i2 m

Centripetal force ii...r

mveBorr

mvevB2

form Eq. (i) and (ii) F 2

mvevB

r or eB ...

mv iir



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8. According to Einstein's theory of relativity, relation between energy of particle and momentum.42

022 cmcpE

0m rest mass of photon (particle)

If we take 0m0

pcE 9. Mass of particle moving with velocity v is given by :

2

20

cv1

mm

Where v velocity of moving particle0m rest mass of particle

c Velocity of light

MCQ QUESTIONSFor the answer of the following questions choose the correct alternative from amongthe given ones.1. Particle A and B have electric charge + q and + 4 q. Both have mass m. If both are allowed to fall

under the same p.d., ratio of velocities A

B

vv

................

(A) 2:1 (B) 1:2 (C) 1:4 (D) 4:12. Energy of photon having wavelength is 2 eV. This photon when incident on metal. maximum

velocity of emitted is v. If is decreased 25% and maximumu velocity is made double, work functionof metal is ........ev(A) 1.2 (B) 1.5 (C) 1.6 (D) 1.8

3. When elctric bulb having 100 W efficiency emits photon having wavelength 410 mm every second,numbers of photons will be...... 1834 ms103c,s.J106h

(A) 100 (B) 1000 (C) 20103 (D) 18103

4. If velocity of free election is made double, change in its de-Broglie wavelength will be......

(A) increase by 2

(B) decrease by 2

(C) increase by 2 (D) decrease 2

5. de-Broglie wavelength of proton accelerated under 100V electric potential difference is 0 . If de -wave length - particle accelerated by the same electric potential differencewill its bouglie ............

(A) 022 (B) 220

(C) 220

(D) 20



238

6. Work function of a body is 4.0 eV. For emission of photoelectron from body, maximum wavelengthof light = ..........(A) 540 nm (B) 400 nm (C) 310 nm (D) 220 nm

7. A body of mass 200 g moves at the speed of 5 m/hr. So de-Broglie wavelength related to it is of theorder........ sJ10626.6h 34

(A) m10 10 (B) m10 20 (C) m10 30 (D) m10 40

8. Photo electric effect on surface is found for frequencies MHz105.5 8 and MHz105.4 8 Ifratio of maximum kinetic energies of emitted photo electrons is 1 : 5, threshold frequency for metalsurface is................(A) MHz1055.7 8 (B) MHz1057.4 8

(C) MHz1035.9 8 (D) MHz1075.5 8

9. For wave concerned with proton, de-Broglie wavelength change by 0.25% . If its momentum changesby PO initial momentum = ........

(A) OP100 (B) 400PO (C) OP401 (D) 100

PO

10. According to Einstein's photoelectric equation, graph of kinetic energy of emitted photo electronsfrom metal versus frequency of incident radation is linear. Its shope.............

(A) depends on type of metal used

(B) depends on intensity of radiation

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

(D) is same for all metals and free from intensity of radiation.

11. Photocell cell is enlightended by small bright source 1 m away. If the same light source is placed

m21 away, number of electrons emitted by cathode will be............

(A) increases twice (B) decreases twice

(C) increases 4 times (D) decreases 4 times

12. If kinetic energy of free electron is made double, change in de-Broglie wavelength will be............

(A) 2 (B) 21

(C) 2 (D) 21

13. Energy corresponding to threshod frequency of metatl is 6.2 eV. If stopping potential correspiondingto radiation incident on srurface is 5V, incident radiation will be in the.....region.

(A) X-ray (B) Ultraviolet (C) infrared (D) Visible



239

14. At C10o temperature, de-Broglie wave length of atom is oA4.0 . If temperature of atom is increased

by C30o , what will be change in de-Broglie wavelength of atom ?

(A) decreaseso

2 A10 (B) decreases o

2 A102

(C) increaseso

2 A10 (D) increases o

2 A102

15. Wavelength of incident radiation on photo sensitive surface is changed from oA4000 to

oA3000 , so

change in stopping potential will be.......

(A) 0.345 V (B) 0.435 V (C) 0.543 V (D) 0.534 V

16. Wavelength of incident radiation on photo sensitive surface is oA4000 If wavelength of this light is

oA3600 , what will be change in kinetic energy of emitted photo electron ?

J106.1ev1,ms103c,s.J10625.6h 191834

(A) 0.52 eV (B) 1.04 eV (C) 2.08 eV (D) 4.16 eV

17. A hollow metalic cubodial has mass 10 kg and length 10 cm. At what speed this cubodial is movedin X-direction so that its de-Broglie wavelength exactly trapped in the cubodial ?

(A) sm101.1 34 (B) s

m102.2 34 (C) sm103.3 34 (D) s

m104.4 34

18. If we take accelerating voltage V = 50 V, electric charge of electron C106.1e 19 and mass of

electron kg101.9m 31 find the wavelength of concerned electrion.

(A)oA1735.0 (B)

oA735.1 (C)

oA35.17 (D) o

A1735

19. What will be energy in eV of photons of - rays having length oA1.0 coming out of excited nucleus

of radium?

sm10625.6h,

sm103c 348

(A) 42.12 (B) 12.42 (C) 22.41 (D) 24.21

20. How many photons of red coloured light having wavelength oA8000 will have same energy as one

photon of violet coloured light of wavelength oA4000 ?

(A) 2 (B) 4 (C) 6 (D) 8



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21. When a radiation of wavelengthoA3000 is incident on metal, 1.85 V stopping potential is obtained .

What will be threshod wave length of metal ?

sm103c,s.J106.6h 834

(A)oA4539 (B)

oA3954 (C)

oA5439 (D)

oA4395

22. Output power of He-Ne LASER of low energy is 1.00 mW. Wavelength of the ligth is 632.8 nm.What will be the number of photons emitted per second from this LASER ?

(A) 115 s1031.8 (B) 115 s1038.5 (C) 115 s1083.1 (D) 115 s1018.3

23. A star which can be seen with naked eye from Earth has intensity 29 Wm106.1 on Earth. If the

corresponding wavelength is 560 nm, and the diameter of the human eye is m105.2 3 , the

number of photons entering in our in 1 s is..............(A) 14 s108.7 (B) 14s1085.8 (C) 15s1085.7 (D) 15s1085.8

24. Find the velocity at which mass of a proton becomes 1.1 times its rest mass,

kg106.1m 27g

Also, calculate corresponding temperature. For simplicity, consider a proton

as non-interacting ideal-gas particle at 1 atm pressure.

183419 ms103c,s.J1063.6h.J106.1eV2

(A) K1075.6T,sm10126v 118 (B) K1065.7T,

sm106.12v 118

(C) K1076.5T,sm1026.1v 117 (D) K1056.7T,

sm106.12v 117

25. Power produced by a star is W104 28 . If the average wavelength of the emitted radiations is

considered to be oA4500 the number of photons emitted in 1 s is...............

(A) 45101 (B) 45109 (C) 45108 (D) 461012

26. What should be the ratio of de-Broglie wavelength of an atom of nitrogen gas at 300 K and 1000 K.

Mass of nitrogen atom is kg107.4 26 and it is at 1 atm pressure Consider it as an idecal gas.

(A) 2.861 (B) 8.216 (C) 6.281 (D) 1.826

27. Wavelength of light incident on a photo - sensitive surface is reduced form

A3500 to 290 mm. The

change in stopping potenital is....... s.J10625.6h 24

(A) V1073.42 2 (B) V1034.27 2 (C) V1042.73 2 (D) V1027.43 2



241

28. An electric bulb of 100 W converts 3% of electrical energy into light energy. If the wavelength of

light emitted is oA6625 , the number of photons emitted is 1 s is........ s.J10625.6h 34

(A) 1710 (B) 1910 (C) 2110 (D) 151029. Work function of Zn is 3.74 eV. If the sphere of Zn is illuminated by the X-ray of wavelength

A12 the maximum potential produced on the sphere is......... sJ3410625.6h (A) 10.314 V (B) 103.14 V (C) 1031.4 V (D) 10314 V

30. Consider the radius of a nucleus to be m10 15 . If an electron is assumed to be in such nucleus, what

ill be its energy ? s.J10625.6h.kg101.9me 3431

(A) 31059.5 (B) 31055.9 (C) 31095.5 (D) 31045.7 31. A proton falls freely under gravity of Earth. Its de Broglie wavelength after 10 s of its mortion is.......,

Neglect the forces other than gravitational force.

s.J10625.6h,kg106.1m,

sm10g 3427

p2

(A)oA96.3 (B)

oA6.39 (C)

oA93.6 (D) o

A3.69

32. Compare energy of a photon of X-rays having oA1 wavelength with the energy of an electron having

same de Broglie wavelength.

34 8 1 19h 6.625 10 J.s, c 3 10 ms , 1ev 1.6 10 J

(A) 8.24 (B) 2.48 (C) 82.4 (D) 24.833. An electron is at a distance of 10 m form a charge of 10 C. Its total energy is 1015.6 10 J . Its de

Broglie wavelength at this point is...................

34 31 9eh 6.625 10 J.s, m 9.1 10 kg. K 9 10 SI

(A)oA87.9 (B) 9.87 Fermi (C)

oA97.8 (D) 8.97 Fermi

34. Wavelength of an electron having energy E is mE2h

0 , where m is the mass of an electron.

Find the wavelength of the elecrton when it centers in X-direction in the region having potential X -

XV If we imaging that due to the potential, electrion enters from one medium to another, what is therefractive index of the medium ?

(A)21

21 E

eVx

eVx

mh2

(B)

2

1

x

21

XEeVE

eVEm2

h

(C) 21

x

21

x

eVEE

m2heVE

(D)

E

eV

eVm2

Eh 21

x

21

x



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35. As shown in the figure, light of energy P (joule) is incident on a small, flat strip of metal of mass m,suspended with the help of weightless string of length l in 1s. All the energy incident on it is absorbedand the strip remains in equillibrium at an angle with respect to vertical. If the light is monochromatic,angle is................

(A)

pcmgtan 1

(B)

cmgptan 1

(C)

pcmgsin 1

(D)

cmgpsin 1

36. U. V. light of wavelength 200 mm is incidenet on polished surface of Fe. work function of the surfaceis 4.5 eV. Find maximum speed of phote electrons.

J106.1eV1,ms103c,s.J10625.6h 191834

(A) sm1075.7 4 (B) s

m10875 5 (C) sm1075.8 4 (D) s

m1075.7 5

37. Light of oA4560 1 mW is incident on photo-sensitive surface of Cs (Cesium). If the quantum

efficiency of the surface is 0.5% what is the amount of photoelectric current produced ?

(A) mA84.1 (B) A18.4 (C) mA18.4 (D) A84.1

38. Work function of metal is 2 eV. Light of intensity 25 Wm10 is incident on 2cm2 area of it. If 1710

electrons of these metals absorb the light, in how much time does the photo electric effectc start ?Consider the waveform of incident light.

(A) s104.1 7 (B) s105.1 7 (C) s106.1 7 (D) s107.1 7

39. Radius of a beam of radiation of wavelength oA5000 is m10 3 . Power of the beam is W10 3 .

This beam is normally incident on a metal of work function 1.9 eV. The charge emitted by the metalper unit area in unit time is...............Assume that each incident photoen emits one elctron.

s.J10625.6h 34

(A) 1.282 C (B) 12.82 C (C) 128.2C (D) 1282 C



243

40. 111011 Photons are icident on a surface in 10 s. These photons correspond to a wavelength ofoA10 . If the surface area of the given surface is 0.01 m2, the intensity of given radiations is...........

sm103c,s.J10625.6h 834

(A) 23

mW1086.21 (B) 2

3

mW10186.2 (C) 2

3

mW106.218 (D) 2

3

mW102186

41. If alpha particale and duetron move with velocity v and 2v, the ratio of their de-Brogle wavelengthwill be.....................

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

42. Uncertainty in position of electron is found of the order of de-Broglie wavelength. Using Heisemberg'suncertainty principle, it is found that order of uncertainty in its velocity = ............

(A) 1 v (B) 2 v (C)2v

(D) v2

43. Photoelectric effect is obtained on metal surface for a light having frequencies 21 f&f where 21 ff .If ratio of maximum kinetic energy of emitted photo electrons is 1 : K , so threshold frequency formetal surface is...............

(A) 1Kff 21

(B) 1KffK 21

(C) 1KffK 12

(D) Kff 12

44. Frequency of incident light on body is f. Threshold frequency of body is f0 . Maximum velocity ofelectron = ..................where m is mass of electron.

(A) 2

1

0

mffh2

(B) m

ffh2 0(C)

21

mhf2

(D) 0ffh

45. If electron is accelerated under 50 KV in microscope, find its de-Broglie wavelength.

(A) m10485.5 12 (B) m10545.8 12 (C) m10585.4 12 (D) m10845.5 12

46. Energy of photon having wavelenth is 2 eV. Maximum velocity of emitted photo electron afterincidence of photon is v. If value of is decreased by 25% and maximum velocity is made double,work function metal will be.................eV.(A) 1.2 (B) 1.5 (C) 1.6 (D) 1.8

47. Energys of photon of light having two different frequencies are 2 eV and 10 eV respectively. If bothare incident on the metal having work function 1 eV, ratio of maximum velocities of emitted electronis.................(A) 1 : 5 (B) 3 : 11 (C) 2 : 9 (D) 1 : 3



244

48. What will be velocity of particle having mass 3 times the rest mass ?

sm103c 8

(A) sm1083.1 8 (B) s

m1092.0 8

(C) sm1083.2 8 (D) s

m1066.5 8

49. De-Broglie wavelength of particle moving at a 41

th of speed of light having rest mass 0m is.........

(A) Cmh87.3

0(B) Cm

h92.4

0(C) Cm

h57.7

0(D) Cm

h46.9

0

50. Work function of metal is 2.5 eV. If wave length of light incident on metal plate is oA3000 , stopping

potential of emitted electron will be.............

sm103c,s.J1062.6h 834

(A) 0.82 V (B) 0.41 V (C) 1.64 V (D) 3.28 V

51. An electron enters perpendicularly into uniform magnetic field having magnitude T105.0 4 . If it

moves on a circular path of radius 2 mm, its de - Broglie wavelength is ......... oA

(A) 3410 (B) 4140 (C) 2070 (D) 278552. In photoelectric effect, work function of mateal is 3.5 eV. By applying - 1.2V potental, photo

electric current becomes zero, so..........(A) energy of incident photon is 4.7 eV.(B) energy of incident photon is 2.3 eV(C) If photon having higher frequency is used, photo electric current is produced.(D) When energy of photon is 2.3 eV, photo electric current becomes maximum

53. Work function of tungsten and sodium are 4.5 eV and 2.3 eV respectively. If threshold wavelengthfor sodium is 5460A, threshold frequnecy for tungsten will be................

(A) Hz1015 (B) Hz101.1 15 (C) Hz102.1 15 (D) Hz104.1 15

54. Ration of momentum of photons having wavelenghth ooA8000&A4000 is..............

(A) 2 : 1 (B) 1 : 2 (C) 20 : 1 (D) 1 : 2055. Work function of metal is 4.2 eV. If ultraviolet radiation (photon) having energy 6.2 eV, stopping

potential will be..................(A) 2 eV (B) 2 V (C) þqLÞ (D) 10.4 V



245

56. If intensity of incident light is increased,.........of photo elctrons will increase.(A) number (B) Frequency (C) energy (D) wavelength

57. A photon having energy 5.5 eV is incident on metal suface and emits photo elctrons having maximumkinetic energy 0.4 eV. Then stopping potential of this electron is..................(A) 5.5 eV (B) 5.1 eV (C) 5.9 eV (D) 4.0 eV

58. Frequency of photon having energy 66 eV is............ s.J106.6h 34

(A) Hz108 15 (B) Hz1012 15 (C) Hz1016 15 (D) Hz1024 15

59. Kinetic energy of proton accelerated under p.d. 1 V will be................(A) 1840 eV (B) 13.6 eV (C) 1 eV (D) 0.54 eV

60. Which of the following phenomenon can not be explained by quantum theroy of light ?(A) Emission of radiation from black body(B) Photo electric effect(C) Polarisation(D) Crompton effect

61. What will be velocity of light of particle having mass double than its rest mass ?

(A) 3c2

(B) 2c

(C)2

c3(D) 4

c3

62. If de-Broglie wavelength of electron is increassed by 1 % its momentum................(A) increases by 1% (B) decreases by 1%(C) increased by 2% (D) decreases by 2%

63. With how much p.d. should an electron be accelerated, so that its de-Broglie wavelength is

A4.0(A) 9410 V (B) 94.10 V (C) 9.140 V (D) 941.0 V

64. de-Broglie wavelength of atom at T K absolute temperature will be....................

(A) mkTh

(B) mKT3h

(C)hmKT2

(D) mKT2

65. Uncertainty of momentum of particle is 130 mskg10 so minimum uncertainty in its position is.........m.

(A) m10 8 (B) m10 12 (C) m10 16 (D) m10 4

66. An electron is accelerated between two points having potential 20 V and 40 V, de- Broglic wavelengthof electron is..................(A)

oA75.0 (B)

oA5.7 (C)

oA75.2 (D) nm75.0

67. Energy of particle having de - Broglie wavelength oA004.0 is...................

(A) 1280 eV (B) 1200 eV (C) 1200 MeV (D) 1200GeV



246

68. de - Broglic wavelength of electron in nth Bohr orbit is............

(A)oA

nr2

(B)oArn2 (C)

oA

n1

(D) oAn

69. If work function of potesium is 3 eV. its threshold wavelength = ..................

s.J106.1eV1,

sm103c.s.J106.6h 19834

(A)oA4125 (B) o

A1860 (C) nm1860 (D) nm4125

70. In photo electric effect, if threshold wave length of a metal is

A5000 work function of this metal

is....................eV. J106.1eV1,s/m103c,s.J1062.6h 19834

(A) 1.24 (B) 2.48 (C) 4.96 (D) 3.72

71. By four photons having frequency 0ff ,..............(A) þqLÞ (B) yuf (C) çku (D) yufÃký Lkrn

72. Work functions for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If threshold wavelength

of sodium is 5460

A , threshold wavelength for tungsten will be......................

A(A) 528 (B) 10683 (C) 2791 (D) 5893

73. Photo senstive surface is incident by light having frequecy 3 times its threshold frequency. In thiscondition, if frequency of light is made half and intensity of light is made doubel, magnitude of photoelectric current becoms........................(A) Fourth (B) double (C) half (D) zero

74. If ratio of threshold frequencies of two metals is 1 : 3, ratio of their work functions is.............(A) 1 : 3 (B) 3 : 1 (C) 4 : 16 (D) 16 : 4

75. It work function of Na and Fe are 2.5 eV and 5eV respectively ratio of their thresholdfrequencies.........................(A) 2 :1 (B) 1 : 2 (C) 125 : 1 (D) 1 : 1

76. If electrion is accelerated under the effect of 200V p.d., its kinetic energy = ...................

(A) J106.1 17 (B) J1023 17 (C) J108.4 17 (D) J104.6 10

77. In quantum mechaincs, a particle.......................(A) can be regarded as group of harmonic waves.(B) can be regarded as a single wave of definite wavelength only(C) Can be regarded as only a pair of two harmonic waves(D) is a point-like object with mass.



247

78. The de-Broglie wavelength of a proton and - particle is same. The ratio of their velocities willbe..............

( particle is the He-nucleus, having two protons and two neutrons. Thus, its mass pm4M wheremp is the mass of the proton.)(A) 1 : 4 (B) 1 : 2 (C) 2 : 1 (D) 4 : 1

79. The de-Broglie wavelength associated with a particle with rest mass 0m and moving with speed oflight in vacuum is..................

(A) cmh

0(B) 0 (C) (D) h

cm0

80. A proton and electron are lying in a box having unpenetrable walls, the ratio of uncertainty in their

velocities are........( em mass of electron and pm mass of proton.)

(A)p

e

mm

(B) pe mm (C) pe mm (D)p

e

mm

81. Photons of enerty 1 eV and 2.5 ev successively illuminate a metal, whose work function is 0.5 eV,the ratio of maximum speed of emitted electrion is..........................(A) 1 : 2 (B) 2 : 1 (C) 3 : 1 (D) 1 : 3

82. A proton and an x-particle are passed through same potential difference. If their initial velocity iszero, the ratio of their de Broglie's wavelength after getting accelerated is...................

(A) 1 : 1 (B) 1 : 2 (C) 2 : 1 (D) 1:22

83. The uncertainty in position of a particle is same as its de-Broglie wavelength, uncertainty in itsmomentum is.......................

(A)

(B)3

2(C)

(D) 2

3

84. Wavelength of an electron having energy 10 keV is.......

A(A) 0.12 (B) 1.2 (C) 12 (D) 120

85. Wavelength A and B are incident on two identical metal plates and photo electrons are emitted.

If BA 2 , the maximum kinetic energy of photo electrons is................

(A) BA KK2 (B) 2KK B

A (C) BA K2K (D) 2KK B

A

86. The de-Broglie wave length of a particle having velosity of 2.25 108 ms–1, is the same value of aphoton wavelength, then the ratio of kinetic energy and photon energy of the particle is ...... (take c= 3 108 ms–1)

(A) 81

(B) 83

(C) 85

(D) 87



248

87. An image of sun is formed by a lens of focal length 30 cm on the metal surface of a photo-electriccell and a photoelectic current (I) is produced. The lens forming the image is then replaced byanother of the same diameter but of focal length of 15 cm. The photoelectric current in this caseis...............

(A) 21

(B) 1 (C) 2I (D) 4I

88. The rationof de - Begli wavelengths of molecules of hydrogen and helium which are at temperature27 and C127 respectively is...................

(A) 21

(B)83

(C)38

(D) 1

89. A photon, an electron and a uranium nucleus all have same wavelength. The one with the msotenergy..................

(A) is the photon

(B) is the electron(C) is the uranium nucleus(D) depends upon the wavelength and properties of the particle.

90. A light of frequency 1.5 times the threshold frequency is incident on photo-sensitive material. If thefrequencey is halved and intensity is doubled, the photoelectric current becomes....................

(A) zero (B) doubled (C) quadrpled (D) halved

91. An electron with rest mass m0 moves with a speed of 0.8 C. Its mass, when it moves with this speedis...............

(A) 0m (B) 6m0 (C) 3

m5 0 (D) 5m3 0

92. The cathode of a photoelectiric cell is changed such that the work function changes from W1 to

122 WWW . If the currents before and after change are I1 and I2 , all other conditionsremaining unchanged, then assuming hf > W2 .............(A) 21 II (B) 21 II (C) 21 II (D) 121 I2II

93. The mass of a particle is 400 times than that of an electron and charge is double. The partcile isacceleratied by 5V. Initially the particle remained at rest, then its final kinetic energy is.................

(A) 5 eV (B) 10 eV (C) 100 eV (D) 2000 eV

94. The work function of a metal is 1 eV. Light of wavelength

A3000 is incident on this metal surface.The maximum velocity of emitted photoelection will be..................

(A) 1ms10 (B) 13 ms10 (C) 14 ms10 (D) 16 ms10



249

95. The work function for tungsten and solidum are 4.5 eV and 2.3 eV respectively. If the threshold

wavelength 0 for sodium is oA5460 the value of 0 for tungsten is....................

(A) oA528 (B) o

A2791 (C) oA5893 (D) o

A1068396. In the Davission and Germer's experiment the filament of electron gun is coated with.........

(A) Cotton (B) BaO (C) Oil (D) FeO

97. Suppose z,y,x represents a particle in three dimensional space, then probility of finding theparticle in the unit volume at a given point x,y,z is .........

(A) inversely proportional to z,y,x (B) directly proportional *

(C) directly proportional to || * (D) inversely proportional to || *

98. Select the correct statement from the following(A) Radiantion and matter (particles) may not exhibit both the wave nature and particle nature

simultaneously at the some moment.(B) At some moment electromagnetic waves get divided in to small pieces named particles(C) In a given circumstance a particle at one moment behaves like particle and the at the next

moment as wave and so on(D) Each microscopic particle is envloped by a wave

99. In which of the following phenomena the photon picture is required ?(A) Energy distribution in black body radiation (B) Compton scattering(C) Photoelectric effect (D) all of the none

100. Two identical detect 25 and 16 photons persecond as shown in the Fig. ...... the ratio of theamplitudes of these light waves.

(A) 1626

(B) 45

(C) 54

(D) 1625

101. Calculate the energy of a photon of radian wavelength oA6000 in eV..

(A) 20.6 eV (B) 2.06 eV (C) 1.03 eV (D) 4.12 eV

102. A 100 W bulb with 10% efficiency is placed at the centre of a sphere (hollow) of radius 41

m.

Find the number of photons arriving on unit area of the surface in the unit time.

(A) 20104 (B) 201051.1 (C) 192 1016 (D) 18104

detector25 photons/s

detector16 photons/s



250

103. The work function of metal is 5.3 eV. What is threshold frequency ?

(A) Hz101.3 15 (B) Hz101.3 45 (C) Hz103.1 15 (D) Hz103.1 45

104. An electron moving with velocity 0.6c, then de-brogly wavelength associated with is...........

(rest mars of electron, Js1063.6hsk101.9m 3431

0 )

(A) m1024.3 12 (B) m104.32 12 (C) m10320 12 (D) m1029.3 14

105. In an experiment to determine photoelectric charactheristics for a metal the intensity of radiation iskept constant. Strating with threshold frequency. Now, frequency of incident radiation is increased.It is observed that ........(A) the nuber of photoelectrons increases (B) the energy of photoelectrons decreases(C) the number of photoelectrons decreases (D) the energy of photoelectrons increases.

106. An oscillator in the walls of cavity in which electromagnetic radiation, has energy equal to 5 h f. Thenthe oscillator is equivalent to ............(A) 2 : 1 (B) 1 : 2 (C) 125 : 1 (D) 1 : 1

107. Valance electrons in metals .......(A) are completely free to move anywhere (B) move in the spave acfording to their

in metal wave function inside the metal.(C) can move outside metal also (D) never escape from metal.

108.Rayleigh and jeans regarded the black body radiations as

(A) TfE 5 (B) TkfE 3 (C) TkfE 5 (D) TfE 4

109. According to Rayleigh and Jeans the black body radiation in the cavity is system of(A) progressive electromagnetic waves (B) standing electromagnetic waves(C) electromagnetic waves of discrete (D) standing waves in lattice

frequencies

110. me of electrons 11 C1.76 10

kg and the stopping potential is 0.71 V, them the maximum velocity of

photo electrons is ........

(A) 1kms150 (B) 1kms200 (C) 1kms500 (D) 1kms250

111. Radius of a nucleus m102 15 . If we imagine an electron inside the nucleus then energy of electronwill be = ......... MeV.

Js106.6h,kg101.9m 3431e

(A) 31098.6 (B) 31094.8 (C) 31098.4 (D) 31048.9



251

112. 2mW light of wave length

A4400 is incident on photo sensitive surface of Cs. If quantum efficiencyis 0.5 %, what will be the value of photoelectric current ?

(A) A56.1 (B) A56.2 (C) A56.4 (D) A56.3

113. A proton, a deutron and an a-particle having thesame momentum, enters a region of uniformelectric field between the parallel plates of acapacitor. The electric field is perpendicular tothe initial path of the particles. Then the ratio ofdeflections suffered by them is(A) 1 : 2 : 8 (B) 1 : 2 : 4(C) 1 : 1 : 2 (D) None of these

114. In the following aggrement y = 1.0 mm, d = 0.24mm and D = 1.2 m. The work function of thematerial of the emitter is 2.2 eV. The stoppingpotential V needed to stop the photon is ..........(A) 0.9 V (B) 0.5 V(C) 0.1 V (D) 0.4 V

115. The difference of kinetic energy of photoelectrons emitted from a surface wavelength

A2500 andoA5000 will be

(A) J1098.1 19 (B) J1098.1 19 (C) eV1096.3 19 (D) .J1096.3 19

Assertion and Reason Type Questions :

Direction : Read the following questions choose if :

(a) Both Assertion and Reason are true and Reason is correct explanantion of Assertion.

(b) Both Assertion and Reason are true, but Reason is not correct explanation of Assertion.

(c) Assertion is true but the Reason is false.

(d) Both Assertion and Reason is false.

116. Assertion :Stopping potential is a measure of K.E. of photo-electrons.

Reason : 2sW eV m K.Ev

(A) a (B) b (C) c (D) d

117. Assertion :Metals like Na or K, emit electrons even when visible lights fall on them .Reason : This is because their work function is low.

(A) a (B) b (C) c (D) d

BrightDark

BrightDark

Bright



252

118. Assertion : The de Broglie wavelength of an electron accelerated through 941 volts is 0.4

A .

Reason : Higher the acceleration potentials of electron, smaller is the de Broglie wavelength.

(A) a (B) b (C) c (D) d

119. Assertion :Photo-electric can take place only with an electron bound in the atom.

Reason : Electron is Fermion and photon is boson.

(A) a (B) b (C) c (D) d

120. Theshold-Frequency is equal to .Hz10................ 14

(A) 4.0 (B) 4.2 (C) 8.0 (D) 8.4

121. An electron is accelerated under a potential difference of 64 V, the de Broglie wave length associated

with electron is oA.............

(Use charge of electon ,C106.1 19 Kg101.9 31 , mass of electron

sec.J10623.6h 34 )

(A) 4.54 (B) 3.53 (C) 2.53 (D) 1.534

122. A particle and proton has same K.E. The ratio of de Broglie wavelength of a particle andproton is....

(A) 41

(B) 21

(C) 1 (D) 2

123. If particle and proton have same momenta, the ratio of de Broglie wavelength of -particle andproton is.....

(A) 41

(B) 21

(C) 1 (D) 2

124. If - particle and proton have same velocities, the ratio of de Broglie wavelength of -particle andproton is ....

(A) 41

(B) 21

(C) 1 (D) 2

125. If - particle and proton are accelerated through the same potential difference, then the ratio of deBrogile wavelength of - particle and proton is ........

(A) 21

(B) 2 (C) 221

(D) 22



253

126. Read the paragraph carefully and select the proper choice from given multiple choices.According to Einstein when a photon of light of frequeny f or wavelength is incident on a photosensitive metal surface of work function . Where hf (here h is Plank's constant) then theemission of photo-electronss place takes place. The maximum K.E. of emitted photo electrons isgiven by hfKmax . If the therehold frequency of metal is 0f then .hf0

(i) A metal of work function 3.3 eV is illuminated by light of wave length 300 nm. The maximum K.E>

of photo-electrons is 34........eV. h 6.6 10 J.sec

(A) 0.825 (B) 0.413 (C) 1.32 (D) 1.65

(ii) Stopping potential of emitted photo-electron is = ...........V.

(A) 0.413 (B) 0.825 (C) 1.32 (D) 1.65

(iii) The threshold frequency fo .Hz10........... 14

(A) 4.0 (B) 4.2 (C) 8.0 (D) 8.4

127. Matching type questions : (Match, Column-I and Column-II property)

Column-I Column-II(A) Planck's theory of quanta (p) Light energy = hv

(B) Einstein's theory of quanta (q) Angular momentum of electron in an orbit.

(C) Bohr's stationary orbit (r) Oscillator energies

(D) D-Broglie waves (s) Electron microscope

(A) sD,rC,qB,pA (B) pD,sC,rB,qA

(C) sD,qC,pB,rA (D) qD,sC,pB,rA


Column-I Column-II(A) Particle nature of light (p) Davisson and Germer

(B) Wave nature of light (q) G. P. Thomson

(C) Wave nature of slow moving electrons (r) Max. Planck

(D) Wave nature of fast moving electrons (s) Muygen

(A) sD,rC,qB,pA (B) pD,sC,rB,qA

(C) qD,pC,sB,rA (D) pD,qC,rB,sA



254


Column-I Column-II(I) Quantisation of charge (P) Diffraction of light

(II) Wave nature of light (Q) de Broglie hypothesis

(III) Dual nature of matter (R) Photo-electric effect

(IV) Particle nature of light (S) Milikan's drop experiment

(A) SIV,RIII,QII,PI (B) RIV,QIII,PII,SI

(C) PIV,SIII,RII,QI (D) OIV,PIII,SII,RI


Column-I Column-II

(I) Energy of photon of wavelength is (P) pE

(II) The be Broglie wavelength associated with (Q) 2chf

particle of momentum P is

(III) Mass of photon in motion is (R)hc

(IV) The velocity of photon of energy E and (S) ph

momentum P is

(A) SIV,RIII,QII,PI (B) PIV,QIII,SII,RI

(C) QIV,PIII,SII,RI (D) PIV,QIII,RII,SI

131. Each of the following questions contains statement given in twocolumns, which have to be matched. The answers to these questionshave to be appropriately dubboed. If the correct matches are A - q,s, B - p, r, C- q, s and D - s then the correctly dubbled matrix willlook like the one shown here :

prr

s

s

q

q

p

q

r

s

p p

p p

p

p

p

p

A

B

C

D



255

Match the statements of column I with that of column II.Column-I Column-II

(A) a-particle and proton have same K.E. a'pp

(B) a-particle has one quarter K.E. then that a'pq

of protot.

(C) a-particle has one quarter K.E. than that a'p pr

of protot.

(D) a-particle and proton has same velocity ap pps

132. In photoelectric effect experiment match the statement of column I with that of column II :Column-I Column-II

(A) When intensity of incident light is increased (p) The value of photo-electric currenton photo-cathode without changing its increases.frequency.

(B) When the frequency of incident light is (q) The value of stopping potential doesincreased on photocathode without not change.changing its intensity.

(C) When the wavelength of incident light is (r) The value of stopping potential does notdecreased without changing its intensity. change.

(D) When the potential of anode is increase (s) The value of photo-electric currentwithout changing the frequency and intensity does not change.of the incident light

133. Photoelectric effect experiments are performed using three different metal plates p, q and r having

work functions ,eV3,eV5.2,eV2 RQp respectively. A light beam containgingwavelengths of 550 nm, 450 nm and 350 nm with equal Intensities illuminates each of the plates. Thecorrect I-V graph for the experiments is.



256

134. The value of stopping potential in the followingdiagram(A) V4 (B) V3(C) V2 (D) V1

135. In the following diagram if 11 VV then........

(A) 21 (B) 21

(C) 21 (D) 21

136. A point source of light is used n an experimenton photoelectric effect. Which of the followingcurves best represent the variation of photocurrent (i) with distance (d) of the source fromthe emitter.(A) a (B) b(C) c (D) d

137. In a parabola spectrograph, the velocities of fourpositive ions P, Q, R and S are u1, u2, u3 and u4

respectively. Then

(A) 4321 vvvv

(B) 4321 vvvv

(C) 4321 vvvv

(D) 4321 vvvv

138. In Thomson spectrograph experiment, fourpositive ions P, Q, R and S are situated on Y-Xcurve a shown in the figure.(A) The specific charge of R and S are same(B) The masses of P and S are same(C) The specific chrage of Q and R are same(D) The velocities of R and S are same



257

139. Kinetic energy of photo electron EK changes with frequency (f) of light. Which of the followinggraph represents this emission ?

140. Which of the following graph shows change in momentum of particle which de-Brogliewavelength ?

141. In a photocell, the curve for current 1 versus potential difference V is best represented by Fig.

142. The curves (a), (b), (c) and (d) show the variation between the applied potential difference (V) andthe photoelectric current (i), at two different intensities of light (I1> I2) In which figure is the correctvariation shown.



258

KEY NOTE1 B 26 D 51 B 76 B 101 B 126(i) A2 D 27 C 52 A 77 A 102 C (ii) B3 C 28 B 53 B 78 D 103 C (iii) C4 B 29 C 54 A 79 B 104 A 127 C5 B 30 B 55 B 80 A 105 D 128 C6 C 31 B 56 A 81 A 106 D7 C 32 C 57 D 82 D 107 B 129 B8 D 33 D 58 C 83 A 108 A 130 B9 C 34 B 59 C 84 A 109 B 13110 D 35 B 60 C 85 B 110 C 13211 C 36 D 61 C 86 B 111 D 133 A12 B 37 D 62 B 87 B 112 D 134 A13 B 38 C 63 D 88 C 113 A 135 D14 B 39 C 64 B 89 A 114 A 136 D15 A 40 B 65 D 90 A 115 D 137 A16 B 41 C 66 C 91 C 116 D 138 A17 B 42 C 67 A 92 A 117 B 139 D18 B 43 B 68 A 93 B 118 C 140 C19 B 44 A 69 B 94 D 119 C 141 C20 A 45 A 70 B 95 B 120 C 142 B21 C 46 D 71 A 96 B 121 D22 D 47 D 72 A 97 C 122 B23 B 48 C 73 B 98 A 123 C24 A 49 A 74 A 99 D 124 A25 B 50 C 75 B 100 B 125 C

1 B 26 D 51 B 76 B 101 B 126(i) A2 D 27 C 52 A 77 A 102 C (ii) B3 C 28 B 53 B 78 D 103 C (iii) C4 B 29 C 54 A 79 B 104 A 127 C5 B 30 B 55 B 80 A 105 D 128 C6 C 31 B 56 A 81 A 106 D 129 B7 C 32 C 57 D 82 D 107 B 130 B8 D 33 D 58 C 83 A 108 A 131 A-q,s B-P,r C-q,s D-q,s9 C 34 B 59 C 84 A 109 B 132 A-p,r B-q,s C-q,s D-r

10 D 35 B 60 C 85 B 110 C 133 A11 C 36 D 61 C 86 B 111 D 134 A12 B 37 D 62 B 87 B 112 D 135 D13 B 38 C 63 D 88 C 113 A 136 D14 B 39 C 64 B 89 A 114 A 137 A15 A 40 B 65 D 90 A 115 D 138 A16 B 41 C 66 C 91 C 116 D 139 D17 B 42 C 67 A 92 A 117 B 140 C18 B 43 B 68 A 93 B 118 C 141 C19 B 44 A 69 B 94 D 119 C 142 B20 A 45 A 70 B 95 B 120 C21 C 46 D 71 A 96 B 121 D22 D 47 D 72 A 97 C 122 B23 B 48 C 73 B 98 A 123 C24 A 49 A 74 A 99 D 124 A25 B 50 C 75 B 100 B 125 C



259

HINT

1. Vqmv21W 2

mqV2v

21

q4q

qq

vv

B

A

B

A

2:1vv

B

A

2. 1...hcmv21

max2

v2'v&75.025.0

2...75.0hcv2m

21 2

max

3hc4c4

33hc8

9hc8

eV2hc

916eV2

98

eV8.1

3.

nhcp

834

9

10310610540100

hcpn

20103



260

4. 2 determent by

12 v2v

K.E. of election 211 mv

21E

21

21

222 v4m

21v2m

21mv

21E

2

12 mv214E

12 E4E

mE2h

E1

22

1E4

EEE 1

21

1

2

1

1

2

2211

1

5. eVmv21 2

meV2pvm 222

meV2hp

me1p

emem pp

p

pe2e,mp4m

81

e2m4em

pp

pp

p

221

p

221

0

220



261

6. J106.14eV4 19

0

hc

hc0

19

834

106.141031062.6

m10103.3 7

m103.310 9

m310

7. sm

36005

hrm5v,kg2.0g200m

mvhp

52.0360010626.6

mvh 34

311085.23

m10385.2 30

m10 30

8. 00max2 ffhhfhfmv

21E

011 ffhE

022 ffhE

Hz105.5MHz105.5f 1481

MHz105.4MHz105.4f 1482

02

01

2

1

ffff

EE

51

EE

2

1

014

014

f105.4f105.5

51



262

014

014 f5105.27f105.4

140 100.23f4

41023f

14

0

Hz1075.5 14

Hz1075.5 8

9. 1...p

0pph

10025.0

2....pp

h100

25.100

0

0ppp

10025.100

p100p25.100p25.100 0

0p25.100p25.0

25.025.100p

0p401p

14. K28327310T1

K31327340T2 o

1 A4.0

mE2h

KT23E nkuðkÚke mKT3

h

T1

2

1

1

2

T

313283

104.0 102



263

951.0104.0 102

102 104.0951.0

o

2 A38.0

12

oooA02.0A4.0A38.0

o2 A102 decreas

15. m104A4000 7o

1

m106.3A3600 7o

2

hceV0

1...hceV1

10

2...hceV2

20

12

102011hceVeV

12

102011

ehcVV

19

834

106.11031062.6

410

6.310 77

6.346.34

6.1362.6

V345.0VV 1020



264

16. m104A4000 7o

1

m103A3000 7o

2

?E

hcE

1...hcE1

1

2...hcE2

2

12

1211hcEE

410

31010310625.6

77834

12110956.19 19

eV04.1E

17. m1030x,kg10m 2

mvhxh

xmhv

2

34

10301010625.6

sm102.2v 34

18. V50v

c106.1e 19

kg101.9m 31e

s.J1062.6h 34

meV2h

50106.1101.921062.6

1934

34

9101735.0 m10735.1 10

oA735.1



265

19. 0A1.0

11

834

1010310625.6hcE

J10875.19 15

J106.1eV1 19

19

15

106.110875.19E

eV1042.12 4

20.1

1hcE

22

nhcE

21 EE

21

nhchc

240008000n

1

2

21.

hceV0

0eVhc

eV85.1106.1103103106.6

197

834

eV85.1125.4

eV275.2

0

hc

hc0

19

834

106.1275.2103106.6

m10439.5 7 oA5439



266

22. W10mW0.1p 3

m108.632nm8.632 9

m108.632nm8.632 9

nhcP

hcpn

834

73

10310625.610328.610

26

10

10875.1910328.6

1610318.0 115 s10318n

23. 29

mW106.11

m106.5nm560 7

m105.2r 3

?n,s1t

AP

AtE1

2r1A1P 69 1025.614.3106.1

W104.31 15

nhcP 834

715

1031062.6106.5104.31

hcpn

41085.8n

25. m105.4A4500,W104P 70

28

nhcnhfnEp

834

728

1031062.6105.4104

hcpn

47109.0

46109



267

26. K300T1

K1000T2

kg107.4m 26

atm1P

KT23mv

21 2

mKT3pvm 222

mKT3p

ph

mKT3h

T1

310

3001000

TT

1

2

2

1

826.12

1

27. ,nm290,A3500 2

o

1

s.J10625.6h 24

0max2 eVhcmv

21

1

10hceV

120

hceV

2

20hceV

12

102011hceVV

21

211020 e

hcVV

9.25.3

6.042.12

7342.0

V1042.73 2



268

28. oA6625

m10625.6 7

sm103c 8

nhfE

nhcE

834

7

10310625.610625.63

hcEn

1910n

29.

hceV0

echcV0

V4.1031V0

30. m102r2x 15

nðu

2hpx

2hp

x

19105274.0

pPm2

pE2

eV1055.9 9 MeV1055.9 3

32.

hcEp

Ep J.1087.19 16

m2h

m2pE 2

22

e

J1041.2E 17e

17

16

e

p

1041.21087.19

EE

4.82EE

e

p



269

34. E K + U

x

2

eVm2

pE

21

xeVEm2p

21xeVEm2

hph

0 h

eVEm2mE2h 2

1

x

21

x

EeVE

35. nhfpE chfp

nc

pp Wòo

CPnp

CPF

1...mgcosT

2...CPsinT

mg1

cP

cosTsinT

cmgPtan

cmgPtan 1



270

36.

hceVmv

21

0max2

7

834

10210310625.6

19106.15.4

19

19

19

19

0 106.1106.15.4

106.11094.9V

5.421.6

V71.1V0

190max

2 106.171.1eVmv21

m1074.22v

19

max2

31

19

max 1011.91048.5v

sm1075.7v 5

max

40. 2o

11 m01.0A,A10,1011N,s10t

t.AE1

NhcE

AtNhcI

1010101010310625.61011I 210

83411

5106.218

23

mW10186.2



271

41. mvh

vm

h

ddd vm

h

v4v22

vmvm dd

d

1d

45. (A)

V1050KV50V 3

meV2h

19331

34

106.11050101.921062.6

22

34

10207.11062.6

m10485.5 12

49. (A)

mvh

ph

2

20

cv1

mm

vm

cv1h

0

2

2

4cv

4cm

c16cc16h

4cm

c16c1

0

2

22

0

2

2

cmh968.04

4cm

h1615

00

cmh87.3

0



272

50. J106.15.2eV5.2 19

m103A3000 7o

s.J1062.6h 34

s.J103c 8

hceVmv

21

02max

eehcV0

52. energy of incident photon is eV7.4

hfEK

KEhf

2.15.3

eV7.4

53. eVe

hchf0

0

0

1

5.4

3.25460T0

N0

N

T

oA2791

00fc

10

8

00 102791

103cf

Hz10075.1 15

Hz10075.1f 150

54.

hP

1P

12

40008000

PP

1

2

2

1

1:2PP

2

1



273

55. 00max2 hfhfeVmv

21

19

190

0 106.1106.12.42.6

ehfhfV

V2V0

57. 0max2 eVmv

21

eV0.4eV0

V0.4V0

58. hfE

34

19

106.6106.166

hEf

Hz1016 15

61. 0

2

20 m2

cv1

mm

21

cv1 2

2

41

cv1 2

2

43

cv

2

2

23

cv

c23v

62. 1 % ½xkzku ÚkkÞ.

ph

p1



274

1p

dppd 2

dpp1d 2

100ppdp100dp

2

%1100dp

decreases by 1%

63. Vem2h

2

2

me2hV

211931

234

104.0106.1101.921062.6

5.940

V941

66. meV2h

V202040VVV 12

20106.1101.921062.6

1931

34

919274.0 oA75.2

67.

2hnx

30

34

1028.61062.6

p2hx

m10054.1 4

m10 4



275

69.0

0hc

00

hc

19

834

0 106.13103106.6

m10125.4 7oA4125

70. 197

834

0 106.11051031062.6

ehc

eV48.2

72. ehchf

00

0

1

xtøkMxLk

MkkurzÞ{

MkkurzÞ{

xtøkMxLk

0

0

MkkurzÞ{xtøkMxLk

MkkurzÞ{xtøkMxLk 00

oA5460

5.43.2

oA2791

74.30

10

20

10

2

1

ff

hfhf

31

2

1

75. 0hf

0f

2

155.2

ff

Fe

Na

Fe0

Na0

2:1



276

76. 200106.1eVmv21 19

max2 J102.3 17

78. p

vm

hvm

h

pp

p

p

mm

vv

pm4m

4mm4

vv

p

pp

1:4vvp

79. mvh

2

20

cv1

mm

vmcv1h

0

2

2

cv , vm

cc1h

0

2

2

0

81. 5.01hfmv21

11

2max

5.05.2hfmv21

22

2max

4

125.0

VV

22max

12max

2:1

21

VV

22max

12max



277

82. 1mp eq p

meV2h

mq1

pp

p

qmqm

e1e24

8

22

1:22p

83.

2hpx

x

p

84. mE2h

19431

34

106.110101.92106.6

m1012.0 10oA12.0

85. mK2p

mK2h

m2hK 2

2

2

1K

2

B

B

2

A

B

B

A

2KK

2KK2 B

A 2

KK BA



278

86.21 1 1mv mv.v PvK.E.of partical 2 2 2

hcK.E.of photon hf hc

8

8

10321025.2

c2v

hc

vh21

38

88.

hcmv

21 2

m

1...)eV(2

ÃkAe,

43hcv4m

21 2

m

382

34

38mv

214 2

m

90. final friquency 000 ff75.0f25.1

therefore photoelectry current is zero

91.2

20

cv1

mm

16

160

10910964.01

m

6.0m

36.0m 00 3

m56m10 00

94.

hcmv

21

max2

eV1106.1100.3

100.31062.6197

834

J19h1002.5eV1375.3

kg101.9m101.9

1020.52V 3131

19

max

Jms1011005.1 166



279

95. 0hf

eVe

hcJhc

00

01

0

0

0

tungsten tungsten 2.3sodium sodium 4.5

o

02.3tungsten 5460A4.5

oA27916.2790

100. 22

21

2

1

AA

ll

1625

45

AA

2

1

101.

ChhfE

7

834

100.6100.31062.6

J1031.3 19

eV106.11031.3

19

19

eV06.2

103. 0hf

Hz1062.6

6.1103.5h

f 34

19

0

Hz103.1 15

104. eV8.3mv21eV max

20

V8.3V0

hfeVmv21

0max2

0

0cchhfhf



280

111. m102r2x 15

2hpx

x2hp

1934

105255.015h10214.32

1066

pPm2

pE2

1931

219

31

219

106.1101.92105255.0J

101.92105255.0

MeV1048.9E 3

112. 3.56 A

tEP

thcnP 1

hctpn1

9834

89

1044.41103106.6

1044102

1nn of 1005.0104.4%5.0 9

552.319h106.17h1022.2neI

A1056.3I 6

113. The deflection suffered bu chared particle in an electric field is

mup

mP

qLEDmu

qLEDy 22

2d

dd2p

ppadp2 p

mq:pmq

y:y:ypqmy

2a

aa

pmq



281

Since pda ppp [Given]

2:1:1q:q:qand4:2:1ma:md:mp adP

8:2:142:21:11y:y:y adp

114. As we know in Young's double slit experiment fringe width = separation between two consecutivefringe or dark fringes

dD

dDy2y2

Here, Dyd2

2.11024.01012 33

o7 A4000m104

Energy of light incident on photo plate

eV1.34000

12375eVE

According to Einstein's photoelectric equation

e

WEVeVWE 0000

V9.0eVe

22.23

115. 2K1K EE 21

12

21

hc11hc

2K1K EE

1010

10834

102500010500010250050001031062.6

.J1096.3 19

120. hf0

34

190

0 106.6106.13.3

hf

150 108.0f Hz100.8f 14

0



282

121. v27.12

533.1827.12

6427.12

oA534.1

122.m2

PK2

Km2p

Km2h

ph

m1

41

mm

x

p

p

21

p

123. ph

pp p

h&phh

ppp

p but PPp

125. vqK

Vqm2vm,Vqmv21 222

Vqm2mv

Vqm2h

mvh



283

qm1

81

m4e2em

mqmq

p

ppp

p

221

p

131. K.E. E mE2mvormv21 2

de-Broglie wavelength, mE2h

mvh

and momentum, mE2mvp

mEh

mEp

(A) When pa EE then

apa

p

p

a or21

41

mm

pap

a

p

a PPSo;214

mm

PP

(B) When ,E41E pa

then 1

4E

4

E1EmEm

p

p

aa

pp

p

a

1E14

E4

EmEm

PP

p

p

pp

aa

p

a

(C) paappa PP&,E4E

(D) pp

a

2pp

2aa

p

apa E4Ea;

14

mm

vm21

vm21

EE,vv

Hence paap PP&



284

133. eV25.2eV550

1240nm55E 1

eV8.2eV450

1240nm450E 2

eV5.3eV350

1240nm350E 3

For metal r, 3 photoelectron

For metal 2 and 3 photoelectron

For metal p; all wavelength are able to generate photoelectron.

Hence photoelectric current will be maximum for p and least for r.

135. 0 02 12 1

w whv hv From the graph v ve e e e

v1as21

136. 2d1I and photo current 2d

1iIi

137. 2

1xd

The ion whose deflection is less, its velocity will be more, From the curve

,xxxx 4321 therefore 4321 vvvv

142. 1 2I I (given) 1 2i i i I and stopping potential does not depend upon intensity

So its value will be same (VO).

• • •



Unit - 17 Important Formula - Studiestoday

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