Dual Nature of Radiation and Matter Book Back Questions & Answers
Unit 8 > Physics > Class 12 > Samacheer Kalvi - English Medium
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1. In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would
a) increase by 2 times
b) decrease by 2 times
c) decrease by 4 times
d) increase by 4 times
Correct answer: c) decrease by 4 times
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2. When a metallic surface is illuminated with radiation of wavelength , the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2 , the stopping potential is V 4 . The threshold wavelength for the metallic surface is (NEET 2016)
a) 4
b) 5
c) 5 2
d) 3
Correct answer: d) 3
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3. A photoelectric surface is illuminated successively by monochromatic light of wavelength and 2 . If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the material is (NEET 2015)
a) hc
b) 2hc
c) hc 3
d) hc 2
Correct answer: d) hc 2
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4. In photoelectric emission, a radiation whose frequency is 4 times threshold frequency of a certain metal is incident on the metal. Then the maximum possible velocity of the emitted electron will be
a) hv m 0
b) 6 0 hv m
c) 2 0 hv m
d) hv m 0 2
Correct answer: b) 6 0 hv m
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5. Two radiations with photon energies 0.9 eV and 3.3 eV respectively are falling on a metallic surface successively. If the work function of the metal is 0.6 eV, then the ratio of maximum speeds of emitted electrons in the two cases will be
a) 1:4
b) 1:3
c) 1:1
d)1:9
Correct answer: b) 1:3
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6. A light source of wavelength 520 nm emits 1.04 1015 photons per second while the second source of 460 nm produces 1.38 1015 photons per second. Then the ratio of power of second source to that of first source is
a) 1.00
b) 1.02
c) 1.5
d) 0.98
Correct answer: c) 1.5
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7. If the mean wavelength of light from sun is taken as 550 nm and its mean power as 3.8 1026W, then the average number of photons received by the human eye per second from sunlight is of the order of
a) 1045
b) 1042
c) 1054
d) 1051
Correct answer: a) 1045
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8. The threshold wavelength for a metal surface whose photoelectric work function is 3.313 eV is
a) 4125
b) 3750
c) 6000
d) 2062. 5
Correct answer: b) 3750
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9. A light of wavelength 500 nm is incident on a sensitive metal plate of photoelectric work function 1.235 eV. The kinetic energy of the photo electrons emitted is (Take h = 6.6 1034 Js)
a) 0.58 eV
b) 2.48 eV
c) 1.24 eV
d) 1.16 eV
Correct answer: c) 1.24 eV
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10. The work functions for metals A, B and C are 1.92 eV, 2.0 eV and 5.0 eV respectively. The metal/metals which will emit photoelectrons for a radiation of wavelength 4100 is/are
a) A only
b) both A and B
c) all these metals
d) none
Correct answer: b) both A and B
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11. Emission of electrons by the absorption of heat energy is calledemission.
a) photoelectric
b) field
c) thermionic
d) secondary
Correct answer: c) thermionic