JEE PHYSICS UNIT 17
QUIZ NO 3
TOTAL QUESTIONS = 20
1. When ultraviolet radiation is incident on a surface, no photoelectrons are emitted. If a second beam causes photoelectrons to be ejected, it may consist of:
A. Infra-red waves
B. X-rays
C. Visible light rays
D. Radio waves
2. A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m, the number of electrons emitted is:
A. Doubled
B. Halved
C. Quartered
D. Unchanged
3. According to Einstein’s photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is:
A. Linear with a positive slope
B. Linear with a negative slope
C. Parabolic
D. Hyperbolic
4. A photosensitive metallic surface has work function, hv₀. If photons of energy 2 hv₀ fall on this surface, the electrons come out with a maximum velocity of 4 ×10⁶ m/s. When the photon energy is increased to 5 hv₀, then maximum velocity of photoelectrons will be:
A. 2 ×10⁷ m/s
B. 2 ×10⁶ m/s
C. 8 ×10⁶ m/s
D. 8 ×10⁵ m/s
5. The work functions for metals A, B, and C are respectively 1.92 eV, 2.0 eV, and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation of wavelength 4100 Å is/are:
A. None
B. A only
C. A and B only
D. All three metals
6. When photons of energy hv fall on an aluminium plate (of work function E₀), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be:
A. 2K
B. K
C. K + hv
D. K + E₀
7. In a discharge tube, ionization of enclosed gas is produced due to collisions between:
A. Negative electrons and neutral atoms/molecules
B. Photons and neutral atoms/molecules
C. Neutral gas atoms/molecules
D. Positive ions and neutral atoms/molecules
8. A photo-cell employs photoelectric effect to convert:
A. Change in the intensity of illumination into a change in photoelectric current
B. Change in the intensity of illumination into a change in the work function of the photocathode
C. Change in the frequency of light into a change in the electric current
D. Change in the frequency of light into a change in electric voltage
9. The momentum of a photon of energy 1 MeV in kg·m/s will be:
A. 7 × 10⁻²⁴
B. 10⁻²²
C. 5 × 10⁻²²
D. 0.33 × 10⁶
10. Monochromatic light of frequency 6.0 × 10¹⁴ Hz is produced by a laser. The power emitted is 2 × 10⁻³ W. The number of photons emitted, on average, by the source per second is:
A. 5 × 10¹⁶
B. 5 × 10¹⁷
C. 5 × 10¹⁴
D. 5 × 10¹⁵
11. A 5-watt source emits monochromatic light of wavelength 5000 Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of:
A. 8
B. 16
C. 2
D. 4
12. The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of incident radiation for which the stopping potential is 5 V lies in the:
A. Ultraviolet region
B. Visible region
C. Infrared region
D. X-ray region
13. In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of:
A. Excitation of electrons in the atoms
B. Collision between the atoms of the gas
C. Collisions between the charged particles emitted from the cathode and the atoms of the gas
D. Collision between different electrons of the atoms of the gas
14. A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3×10⁶ m/s. The velocity of the particle is:
A. 2.7×10⁻¹⁸ m/s
B. 9 × 10⁻² m/s
C. 3 × 10⁻² m/s
D. 2.7 × 10⁻² m/s
15. The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (kelvin) and mass m, is proportional to:
A. √T
B. T
C. 1/√T
D. 1/T
16. Electrons of mass m with de-Broglie wavelength λ fall on the target in an X-ray tube. The cutoff wavelength (λ₀) of the emitted X-ray is:
A. λ₀ = λ
B. λ₀ = 2λ
C. λ₀ = λ/2
D. λ₀ = λ/4
17. Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, the maximum energy of emitted photoelectrons will be:
A. 2 eV
B. 3 eV
C. 4 eV
D. 1 eV
18. An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is:
A. 1:1
B. 1:√2
C. √2:1
D. 2:1
19. When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V/4. The threshold wavelength for the metallic surface is:
A. 3λ
B. 4λ
C. 5λ
D. 2λ
20. Light of wavelength 500 nm is incident on a metal with work function 2.28 eV. The de Broglie wavelength of the emitted electron is:
A. 1.23 nm
B. 2.46 nm
C. 0.61 nm
D. 3.69 nm
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