Question

Two beams of coherent light are shining on the same piece of white paper. with respect to the crests and troughs of such waves, darkness will occur on the paper where

Answer 1

Answer:

"where crests and troughs have their maxima at the same time"

Crests and troughs are 180 deg out of phase and when they have their maxima at the same time and place, their net contribution will be zero"