Question

At points of constructive interference with maximum intensity of two coherent monochromatic waves (wavelength λ), the path difference between them is 

(A) zero or an integral multiple of λ 

(B) zero or an integral multiple of λ/2 

(C) zero or an even integral multiple of λ/2 

(D) an odd integral multiple of λ/2.

Answer 1

(A) zero or an integral multiple of λ