When a central dark fringe is observed in reflection in a circular interference pattern, waves reflected from the upper and lower surfaces of the medium must have a phase difference, in radians, of
A) 0.
B) π/2.
C) π.
D) 3π/2.
E) 2π.

Question

Quizplus · Accepted Answer

In order for a central dark fringe to be observed in a reflection interference pattern, the waves reflected from the upper and lower surfaces of the medium must be 180 degrees out of phase, which is equivalent to a phase difference of π radians. Therefore, the correct answer is choice C, π.

When a Central Dark Fringe Is Observed in Reflection in a Circular