2nd Year Physics Chapter 7 Test21. Quantum Physics

Q1. Multiple choice questions (Attempt all · 10 × 1 = 10)

1. Increasing the intensity of incident light of constant frequency above the threshold frequency results in:
   1. Increase in photoelectric current
   2. Increase in kinetic energy of electrons
   3. Both a and b
   4. No change
2. The energies of whole electrons in photoelectric effect
   1. change with intensity of light
   2. change with velocity of light falling on the metal surface
   3. change with frequency of light
   4. none of the above
3. The process of pair production takes place if the energy of photon is
   1. equal to 2mₒc²
   2. less than threshold
   3. greater than 2mₒc²
   4. none of these
4. The minimum frequency of light required to emit electrons from a metal surface is called:
   1. Cut-off frequency
   2. Threshold frequency
   3. Critical frequency
   4. Surface frequency
5. The speed of an electromagnetic wave in space is approximately:
   1. 3×10¹⁰ m/s
   2. 3×10⁸ m/s
   3. 3×10⁶ m/s
   4. 3×10⁵ m/s
6. Which of the following has the longest wavelength?
   1. x-rays
   2. Infrared waves
   3. Microwaves
   4. Radio waves
7. The wavelength of visible light used in optical microscopes is in the range of:
   1. 100–200 Å
   2. 4000–7000 Å
   3. 1–10 Å
   4. 0.01–0.1 Å
8. The energy of the photon of wavelength 500 nm is:
   1. 3.10 eV
   2. 2.49 eV
   3. 1.77 eV
   4. 1.52 eV
9. The process of pair production will take place if the energy of photon is
   1. 0.21 MeV
   2. 0.51 MeV
   3. 1.21 MeV
   4. 1.02 MeV
10. The discrete energy levels in an atom are explained by:
    1. Newton’s law
    2. Bohr’s model
    3. Rutherford’s model
    4. Thomson’s model