F Sc (2nd year) Physics MCQ’s Chapter # 20

CHAPTER # 19. DAWN OF MODERN PHYSICS

1. The Einstein mass-energy relationship is
a) 𝐸 = 𝑚𝑐 10. A positron is a particle having
b) 𝐸 = 𝑚𝑐 3 a) Mass equal to electron
c) 𝐸 = 𝑚𝑐 2 b) Charge equal to electron
d) 𝐸 = 𝑚2 𝑐 2 c) Equal mass but opposite charge to electron
d) Mass equal to proton
2. When an electron combines with a positron,
we get 11. In compton scattering, the compton shift ∆𝜆
a) One photon will be equal to compton wavelength if the
b) Two photons scattering angle is
c) Three photons a) 0°
d) Four photons b) 45°
c) 60°
3. Production of X-rays can be regarded as the d) 90°
reverse phenomenon of
a) Pair production 12. Unit of plank’s constant is
b) Photoelectric effect a) volt
c) Compton effect b) J s
d) Annihilation of matter c) J s−1
d) 𝑒𝑉
4. The radius of atom is the order of
a) 1010 𝑚 13. Which one is most energetic?
b) 10−10 𝑚 a) 𝛾 − 𝑟𝑎𝑦𝑠
c) 10−14 𝑚 b) 𝑋 − 𝑟𝑎𝑦𝑠
d) 1014 𝑚 c) 𝑈𝑙𝑡𝑟𝑎𝑣𝑖𝑜𝑙𝑒𝑡 𝑟𝑎𝑦𝑠
d) 𝑉𝑖𝑠𝑖𝑏𝑙𝑒 𝑙𝑖𝑔𝑕𝑡
5. In 1905, the special theory of relativity was
proposed by 14. The total amount of energy radiated per unit
a) Maxwell orifice area of cavity radiator per unit time is
b) De Broglie directly proportional to
c) Bohr a) 𝑇
d) Einstein b) 𝑇 2
c) 𝑇 3
6. Neutron was discovered in 1932 by d) 𝑇 4
a) Bohr
b) Chadwick 15. Plank’s constant h has the same units as that of
c) Dirac a) Linear momentum
d) Fermi b) Angular momentum
c) Torque
7. The rest mass of photon is d) Power
a) Infinity
b) Zero 16. Photoelectric effect was explained by
c) 𝑕𝑓 a) Hertz
d) 𝑚𝑐 2 b) Einstein
c) Rutherford
8. A maximum compton shift in the wavelength d) Bohr
of scattered photon will be occur at
a) 𝜃 = 0° 17. All motions are
b) 𝜃 = 45° a) Absolute
c) 𝜃 = 90° b) Uniform
d) 𝜃 = 180° c) Relative
d) Variable
9. The Davisson and Germer experiment 18. The rest mass energy of an electron in MeV is
indicates equal to
a) Interference a) 0.511
b) Polarization b) 0.611
c) Electron diffraction c) 0.902
d) Refraction d) 1.02
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F Sc (2nd year) Physics MCQ’s Chapter # 20

19. An observer shoots parallel to a meter stick at 27. The minimum energy needed for a photon to
very high speed (relativistic) and finds that the create an electron-positron pair is
length of meter stick is __________ a) 1.02 KeV
a) Greater than one meter b) 0.51 KeV
b) Less than one meter c) 0.51 MeV
c) One meter d) 1.02 MeV
d) None of these
28. Davisson and Germer indicates
20. Linear momentum of a photon is _____________ in their experiment
a) Zero a) Electron refraction
b) hf/c2 b) Electron polarization
c) hf/c c) Electron reflection
d) c2/hf d) Electron diffraction

21. Photon with energy greater than 1.02 MeV can 29. In Davison – Germer experiment, the
interact with matter as diffracted proton from crystal shows
a) Photoelectric effect ____________
b) Compton effect a) Particle property
c) Pair production b) Wave property
d) Pair annihilation c) Light property
d) Quantum property
22. Stopping potential for a metal surface in case
of photo electric emission depends on 30. In electron microscope, electric and magnetic
a) The threshold frequency for the metal field are used as _______
surface a) Electromagnetic gun
b) The intensity of incident light b) Source of electromagnetic waves
c) The frequency of incident light and the c) Deflected charged particle
work function for metal surface d) Converging source of electrons
d) None of these
31. The uncertainty in momentum and position is
23. As the temperature of black body is raised, the due to its ___________
wavelength corresponding to maximum a) Property of matter and radiation
intensity b) Two dimensional motions
a) Shifts towards longer wavelength c) Emotion of certain wave length
b) Shifts towards shorter wavelength d) Very high velocity
c) Remains the same
d) Shifts towards shorter as well as longer 32. The energy radiated is directly proportional to
wavelength fourth power of Kelvin’s temperature is _____
a) Karl-wein’s laws
24. The name of photon for quantum of light was b) Raleigh jeans law
proposed by c) Stephens law
a) Ampere d) Planck’s
b) Planck’s
c) Thomson 33. The anti-particle of electron is
d) Einstein a) Proton
b) Position
25. A photon is a ____________ c) Meson
a) Unit of energy d) Neutron
b) Positively charged particle
c) Packet of electromagnetic radiations 34. The reverse process of pair-production is
d) Unit of wavelength a) Annihilation
b) Materialization
26. The light of suitable frequency falling on matel c) Fission
surface ejects electrons, this phenomenon is d) Fusion
called 35. The decrease in length with speed was
a) X-ray emission explained by
b) Compton effect a) Einstein
c) Photoelectric effect b) Lorentz
d) Nuclear fission c) Bohr
d) None

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F Sc (2nd year) Physics MCQ’s Chapter # 20

36. All the motion in this universe are 45. Application of photoelectric effect is
a) Absolute a) Photo diode
b) Uniform b) Photo transistor
c) Variable c) Photocell
d) Relative d) None of these

37. Pair production cannot possible in 46. In Compton effect, the law/laws are conserved
a) Air a) Energy
b) Water b) Momentum
c) Glass c) Both
d) Vacuum d) None of these

38. The minimum energy required for pair 47. The equations of pair production is
production is a) hf = 2moc2 – KE(e-) + K.E (e+)
a) 10.2 Mev b) hf = 2moc2 + KE(e-) + K.E (e+)
b) 1.02 Mev c) hf = 2mo2c2 + KE(e-) + K.E (e+)
c) 102 Mev d) hf = 2mo2c + KE(e-) + K.E (e+)
d) None
48. Which of the following has the same

39. The relation Max
T  Contt .
is
dimension as h/moc?
a) Length
a) Wein’s Law b) Time
b) Plank’s Law c) Mass
c) Stephen Law d) None
d) None
49. Photon ‘A’ has twice the energy of photon ‘B’.
v2 What is the ratio of the momentum of ‘A’ to
40. A quantity 1  2 is always that of ‘B’?
c a) 4 : 1
a) Greater than one b) 2 : 1
b) Less than one c) 1 : 2
c) Equal to one d) None
d) None of these
50. Electron is an antiparticle of
41. Who gave the idea of matter wave? a) Proton
a) De-Broglie b) Photon
b) Planck c) Positron
c) Einstein d) Deuteron
d) Huygen

42. The Stefen-Boltzmann’s constant has the value

a) 5.67 × 10-5Wm-2K-4
b) 5.67 × 10-6Wm-1K-4
c) 5.67 × 10-6Wm-2K-4
d) 5.67 × 10-8Wm-2K-4

43. The energy of photon of radio waves is only

about
a) 10-6eV
b) 10-4eV
c) 10-10eV
d) 10-12eV

44. The idea of quantization of energy was

proposed by
a) Einstein
b) Max Planck
c) Compton
d) None of these