Laser Multiple Choice Questions and Answers

1 Which of the following can be used in a vibrational analysis of structure?

A Laser

B Maser

C Quarts

D Electrical waves

View Answer

Answer: Laser

2 Which of the following is used in atomic clocks?

A Laser

B Quartz

C Maser

D Helium

View Answer

Answer: Maser

3 What is the need to achieve population inversion?

A To excite most of the atoms

B To bring most of the atoms to ground state

C To achieve stable condition

D To reduce the time of production of laser

View Answer

Answer: To excite most of the atoms

4 Which of the following can be used for generation of laser pulse?

A Ruby laser

B Carbon dioxide laser

C Helium neon laser

D Nd- YAG laser

View Answer

Answer: Nd- YAG laser

5 Calculate the number of photons, from green light of mercury (ʎ = 4961 Å),required to do one joule of work.

A 4524.2×1018/m3

B 2.4961×1018/m3

C 2.4961/m3

D 2.4961/m

View Answer

Answer: 2.4961×1018/m3

6 Calculate the wavelength of radiation emitted by an LED made up of a semiconducting material with band gap energy 2.8eV.

A 2.8 Å

B 4.3308 Å

C 5548.4 Å

D 4430.8 Å

View Answer

Answer: 4430.8 Å

7 Which of the following is an example of optical pumping?

A Ruby laser

B Helium-Neon laser

C Semiconductor laser

D Dye laser

View Answer

Answer: Ruby laser

8 Which of the following is a unique property of laser?

A Directional

B Speed

C Coherence

D Wavelength

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Answer: Coherence

9 A device which converts electrical energy in the form of a current into optical energy is called as

A Optical source

B Optical coupler

C Optical isolator

D Circulator

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Answer: Optical source

10 How many types of sources of optical light are available?

A One

B Two

C Three

D Four

View Answer

Answer: Three

11 The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation? E =E2 – E1 = hf

A Gravitation constant

B Planck’s constant

C Permittivity

D Attenuation constant

View Answer

Answer: Planck’s constant

12 The radiation emission process (emission of a proton at frequency) can occur in __________ ways.

A Two

B Three

C Four

D One

View Answer

Answer: Two

13 Which process gives the laser its special properties as an optical source?

A Dispersion

B Stimulated absorption

C Spontaneous emission

D Stimulated emission

View Answer

Answer: Stimulated emission

14 An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate.

A 3×10-13

B 1.47×10-11

C 2×10-12

D 1.5×10-13

View Answer

Answer: 1.47×10-11

15 The lower energy level contains more atoms than upper level under the conditions of ________________

A Isothermal packaging

B Population inversion

C Thermal equilibrium

D Pumping

View Answer

Answer: Thermal equilibrium

16 __________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.

A Light amplification

B Attenuation

C Dispersion

D Population inversion

View Answer

Answer: Light amplification

17 A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes.

A 1×102

B 3×106

C 2.9×105

D 2.2×105

View Answer

Answer: 2.2×105

18 A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.

A 2.8 GHz

B 1.2 GHz

C 1.6 GHz

D 2 GHz

View Answer

Answer: 1.6 GHz

19 An injection laser has active cavity losses of 25 cm-1and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm.

A 46 cm-1

B 51 cm-1

C 50 cm-1

D 49.07 cm-1

View Answer

Answer: 49.07 cm-1

20 Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser.Frequency separation = 2GHz Wavelength = 0.5 μm.

A 1.4×10-11

B 1.6×10-12

C 1×10-12

D 6×10-11

View Answer