Question

When is the wave interference strong?

(a) When the paths taken by all of the interfering waves are greater than the coherence length

(b) When the paths taken by all of the interfering waves are lesser than the coherence length

(c) When the paths taken by all of the interfering waves are equal than the coherence length

(d) When the paths taken by all of the interfering waves are independent of the coherence length

This question was addressed to me in an internship interview.

My doubt stems from Coherent and Incoherent Addition of Waves in chapter Wave Optics of Physics – Class 12

Answer 1

The correct answer is (b) When the paths taken by all of the interfering waves are lesser than the coherence length

Explanation: Coherence length is defined as the propagation distance over which a coherent wave maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves are lesser than the coherence length.