CBSE Physics Electrons and Photons Test 1 Online

1. When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however, light of 600 nm wavelength is sufficient for creating photoemission, what is the ratio of the work functions of the two emitters ?

2. The cathode of a photoelectric cell is changed such that the work function changes from W₁ to W₂ (W₂ > W₁). If the current before and after changes are l₁ andl₂, all other conditions remaining unchanged, then (assuming hv > W₂) ?

3. Number of ejected photoelectron increases with increases  ?

4. The energy of a photon of wavelength λ is ?

5. Gases begin  to conduct electricity at low pressure because ?

6. The wavelength of a 1 KeV photon is 1.24 x 10^-9m. What is the frequency of 1 MeV photon ?

7. Which of the following is true ?

8. Ultraviolet radiation of 6.2eV falls on an aluminum surface. KE of fastest electron emitted is (work function = 4.2 eV) ?

9. Which of the following are thermions ?

10. If the threshold wavelength for a certain metal is 2000 A°, then the work function of the metal is ?

11. The momentum of a photon of an electromagnetic radiation is 3.3 x 10^-29 kg-ms^-1. What is the frequency of the associated waves ((h = 6.ò x 10^-34 j-s, c = 3 x 10⁸ ms^-1) ?

12. The wavelength associated with an electron, accelerated through a potential difference of100 V, is of the order of ?

13. Kinetic energy of an electron which is accelerated in a potential difference of 100 V is ?

14. The threshold frequency for photoelectric effect on sodium corresponds to a wavelength of 5000 A°. Its work function is ?

15. The 21 cm radiowave emitted by hydrogen is interstellar space is due to the interaction called the hyperfine in atomic hydrogen. The energy of the emitted wave is nearly ?