Question

A laser beam is coherent because it contains

• A. waves of several wavelengths.
• B. incoherent waves of a single wavelength.
• C. coherent waves of several wavelengths
• D. coherent waves of a single wavelength.

Answer 1

The correct option is D

coherent waves of a single wavelength.

Explanation for the correct option(s):

D: coherent waves of a single wavelength.

1. Laser is the short form of light amplification by stimulated emission of radiation.
2. Laser beam is intense, monochromatic (that is of the single wavelength) collimated and highly coherent.

Explanation for the incorrect option(s):

A: waves of several wavelengths.

Laser beam consists of waves of exactly the same wavelength in phase.

B: incoherent waves of a single wavelength.

Laser beam is highly coherent.

C: coherent waves of several wavelengths

Laser beam is highly coherent of single wavelengths.

Hence, A laser beam is coherent because it contains coherent waves of a single wavelength.

Option D is correct.