Question

Laser beams are used to measure long distances because
A. They are monochromatic
B. They are highly polarised
C. They are coherent
D. They have high degree of parallelism

Answer 1

Correct Answer - d
Laser beam are perfectly parallel. So that they are very narrow and can travel a long distance without spreading. This is the feature of laser while they are monochromatic and coherent thes are charactristics only.