Unit5

1. LASER is the short form of(A) Light Amplification by Stimulated Emission of Radiation(B) Light Amplification by Spontaneous Emission of Radiation(C) Light Absorption by Spontaneous Emission of Radiation(D) Light Absorption by Stimulated Emission of Radiation

2. Which one of the following is not a characteristic of a LASER beam(A) Monochromaticity (B) Coherence (C) Directionality (D) Stability

3. Which one of the following processes is not taking place during the interaction of radiation with matter(A) Diffusion (B) Spontaneous emission (C) Stimulated emission (D) Induced absorption

4. The relation between Einstein coefficients is(A) R21 = A21N2 (B) R’21 = B21N2u(n) (C) B12 = B21 (D) B21/A21 = 8phn3/c3

5. The component of the laser system which provides a sort of feedback is(A) Pumping mechanism (B) Resonant cavity (C) Metastable state (D) Active medium

6. Which of the following is a feature of a laser system(A) Metastable state (B) Population inversion (C) Cavity Resonators (D) All of the these

7. Pumping mechanism employed in He-Ne laser is(A) Optical pumping (B) Direct electron excitation and inelastic atom-atom collisions(C) Heat pumping (D) Chemical pumping

8. Which one of the following is false(A) Very high pump power required in three level laser system(B) Ruby laser is an example of four level laser system(C) Population inversion can easily achieved with lower pumping requirements in four level laser systems(D) Semiconductor laser is not an example of three level laser system.

9. The popular line of He-Ne laser is(A) 632.8 nm (B) 1.15 mm (C) 3.39 mm (D) 623.8 nm

10. Plane polarized laser output in He-Ne laser is due to(A) Brewster windows (B) Resonant cavity (C) Direct electron excitation(D) Metastability

11. In He-Ne laser, the discharge tube is filled with a mixture of Helium and Neon gases in the weight ratio(A) 10:1 (B) 1:10 (C) 10: 0.1 (D) 0.1:10

12. The material used for the fabrication of semiconductor laser is(A) Silicon (B) Germanium (C) Gallium Arsenide (D) Gallium

13. In semiconductor laser, laser light is due to(A) Spontaneous emission (B) Electron-hole recombination (C) Electrical pumping(D) Fermi energy

14. The commonly used lasers in industry are(A) Nd:YAG laser and CO2 laser (B) Ruby laser and semiconductor laser (B) Diode laser and Gas dynamic laser (D) He-Ne laser and semiconductor laser

15. Laser is used in(A) RADAR (B) SONAR (C) LIDAR (D) POLYMER

16. For the study of atmospheric pollutants, researchers use(A) Newton’s laws (B) Relativity principle (C) Compton effect (D) Raman effect

17. The idea of holography was first developed by(A) Maimann (B) Gabour (C) Kamerlingh ones (D) Young

18. The basic principle of Holography is(A) Polarisation (B) Diffraction (C) Interference (D) Reconstruction

19. Hologram gives(A) Two dimensional image (B) Three dimensional image (C) Laser light (D) Polarized light

20. Which one of the following is not an application of holography(A) Pattern recognition (B) Dynamic aerosol camera (C) Fog droplet camera (D) Measurement of atmospheric pollutants