Laser Multiple Choice Questions and Answers

Laser Multiple Choice Questions and Answers

Q. Which of the following is a unique property of laser?
a) Directional
b) Speed
c) Coherence
d) Wavelength

Answer: c

Q. The number of photons emitted for a 2.5 mW He-Ne laser is ________.

a) 4.9 × 1015

b) 5.9 × 1015

c) 6.9 × 1015

d) 7.9 × 1015

Ans: d) 7.9 × 1015

Q. Which of the following is an example of optical pumping?
a) Ruby laser
b) Helium-Neon laser
c) Semiconductor laser
d) Dye laser

Answer: a

Q. When laser light is focussed on a particular area for a long time, then that particular area alone will be heated.
a) True
b) False

Answer: a

Q. 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: d

Q. If there are ‘N’ atoms in a source, each emitting light with intensity ‘I’, then the total intensity produced by an ordinary source is proportional to ‘NI’, whereas in a laser source, it is proportional to ________.

  1. (NI)2
  2. 2NI
  3. NI2
  4. N2I

Ans: Option 4 : N2I

Q. 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

Answer: b

Q. Which of the following can be used for the generation of laser pulse?
a) Ruby laser
b) Carbon dioxide laser
c) Helium-neon laser
d) Nd- YAG laser
Answer: d

Q. 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

Answer: a

Q. Laser is called as a non-material knife.
a) False
b) True

Answer: b

Q. In a Ruby laser, the colour of laser light is due to_____  atom.

  1. Oxygen
  2. Aluminium
  3. Xenon
  4. Chromium

Ans: Option 4 : Chromium

Q. DVD uses the laser.
a) True
b) False

Answer: a

Q. Which of the following is used in atomic clocks?
a) Laser
b) Quartz
c) Maser
d) Helium

Answer: c

Q. Which of the following can be used in the vibrational analysis of structure?
a) Maser
b) Quarts
c) Electrical waves
d) Laser

Answer: d

Q. Laser Rays are :

a. instrument to measure the velocity of the aeroplane

b. instrument to measure the intensity of X-rays

c. measure of frequency

d. highly coherent waves

Ans: d) highly coherent waves

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