Monochromatic light in air reflects from the upper (air–film) surface and the lower…
PHYSICS · Single correct · A Level · Physics · Waves · Waves
Problem
Monochromatic light in air reflects from the upper (air–film) surface and the lower (film–substrate) surface of a thin transparent film whose index of refraction lies between that of air and that of the glass substrate beneath it. Which of the following best describes the phase shifts that the two reflected rays experience upon reflection?
(a) Only the ray reflected at the upper surface undergoes a half-cycle (πrad) phase shift.
(b) Neither reflected ray undergoes a half-cycle (πrad) phase shift.
(c) Both reflected rays undergo a half-cycle (πrad) phase shift.
(d) Each reflected ray undergoes a half-cycle phase shift of opposite sign, so the net phase difference between them is zero.