1. 1LASER is a short form of a) Light amplification by stimulated absorption radiation b) Light amplification by stimulated emission of radiation c) Light absorption by spontaneous absorption of radiation d) Light absorption by spontaneous emission of radiation 2Laser beam is made of a)Electronsb)Highly coherent photons c)Very light and elastic particlesd)None of them

2. 3In the population inversion a) The number of electrons in higher energy state is more than the ground state b) The number of electrons in lower energy state is more than higher energy state c) The number of electrons in higher and lower energy state are same d)None of them 4The characteristics of laser beam : a)Highly directionalb)Highly intense c)Highly monochromaticd)All of them

3. Which event is likely to take place when a photon of energy equal to the difference in energy between two levels is incident on a system? a)Absorptionb)Emission c)Absorption and emissiond)None of the above Which one of the following laser have highest efficiency? a)Rubyb)Semiconductor b)He-Ned)None of above

4. The method of population inversion to the laser action in He-Ne laser is a)Atomic collisionb)Direct conversion b)Electric discharged)Electron impact In spontaneous emission the atoms or molecules in the higher energy state E 2 eventually return to the ground state by emitting their excess energy spontaneously. The rate of spontaneous emission is a)Directly proportional to population of the energy level E 2. b) Directly proportional to population of the energy level E 1. c)Inversely proportional to population of the energy level E 2. d)None of the above

5. In stimulated emission, a photon having energy E equal to the difference in energy between two levels E 2 and E 1., stimulate an atom in the higher state to make a transition to the a)Lower energy state with a creation of second photon. b) Metastable state with creation of second photon. c)Higher energy state with a creation of two photons. d)None of the above The rate of spontaneous emission depends upon the number of atoms in the a)Excited stateb)Lower state c)Metastable stated)None of the above

6. The spontaneous emission produces Coherent lightb)Incoherent light White lightd)None of the above The material in which population inversion can take place is called Active mediumb)Passive medium Gaseous mediumd)Vapour medium

7. In case of population inversion, the number atoms is more in higher energy state than a)In the lower energy stateb)In the metastable state c)In the middle stated)None of them The process of raising the atoms from a lower energy state to higher, to create population inversion a)Pumpingb)Exothermic reaction c)Endothermic reactiond)None of the above

8. In case of optical pumping, an external optical source like Xenon’ flash lamp is employed to produce a) High population in the higher energy level of laser medium b) Low population in the higher energy level of laser medium c) Higher population in the lower energy level of laser medium d) lower population in the metastable state of laser medium Optical pumping is suitable for any medium which is a)Transparent to lightb)Not transparent to light c)Metallicd)None of the above

9. In a semiconductor laser, electrical energy is directly converted to a)Light energyb)Sound energy c)Heat energyd)Nuclear energy An optical resonator plays a major role in the generation of the a)Excited atoms between the mirrorsb)Laser output c)More number of excited atoms or photonsd)All of them

10. Ruby laser is a solid state laser, the active medium is a)Crystalline substanceb)Non crystalline substance c)Gaseous substanced)None of the above In case of ruby laser, optical resonator cavity is formed by the silvered ends of 1M a)Ruby crystalb)The Calcium crystal c)Tourmaline crystald)Quartz crystal

11. Ruby laser works in the a)Pulsed modeb)Non pulse mode c)Continuous waved)None of the above In He-Ne laser the common Wave length of laser is a)6328A 0 b)6943A 0 c)10600A 0 d)None of the above

12. Ruby is crystalline substance of Aluminum oxide doped with a) Approximately 0.05% by weight of Chromium oxide. b) Approximately 0.5% by weight of Chromium oxide. c) Approximately 0.02% by weight of Chromium oxide. d) Approximately 0.01% by weight of Chromium oxide. The main advantage of gas lasers is that a) They can operated continuously b) They cannot be operated continuously c)They can operated in the pulse mode d)None of the above

13. In case of semiconductor lasers the laser transition is possible only in a) Indirect band gap semiconductors b)Direct band gap semiconductors c) Both direct as well as indirect band gap semiconductors d)None of the above Which of the following conditions is very essential for the production of laser light? 1M a) Spontaneous emission process b)Stimulated emission process c)Population inversion processd)All of them

14. Which of the following is not a pumping process? a)Optical pumpingb)Electrical pumping c)Chemical pumpingd)Thermal pumping Which of the following is not a laser property? a)Coherenceb)Highly directional c)Extreme brightnessd)Divergence

15. In Ruby laser which ions give rise to the laser action? a)AL 2 O 3 b)Al 3+ c)Cr 3+ d)None of the above The population inversion takes place at ………………..medium. a)Activeb)Passive c)Moderated)none of the above

18. Example of solid-state laser is ……………… a)Na-crystalb)Ruby crystal c)Iron crystald)none of the above In a Ruby laser, the laser action is achieved by ………… a)optical pumpingb)electrical pumping c)gas discharged)none of the above method.

19. The active medium of a helium-neon laser is made up of......... ratio of helium-neon. 1M a)10:2b)10:1 c)10:3d)10:49 Diode laser consists of.….......... doped in a single crystal. a)p-n junctionb)p type c)n-typed)none of the above

20. Ruby laser radiates an intense pulse laser of wavelength ………… a)6943 Ab)5896 A c)6328 Ad)6334 A The light source used for optical pumping ………….. a)Xenon or Kryptonb)Neon or Krypton c)Argon or Neond)none of the above.

21. The active medium of a helium-neon laser is made up of......... ratio of helium-neon. 1M a)10:2b)10:1 c)10:3d)10:49 Diode laser consists of.….......... doped in a single crystal. a)p-n junctionb)p type c)n-typed)none of the above