Light is normally incident on a thin soap film and is reflected. If the wavelength of this light is "L" and the index of refraction of the soap film is "N", complete destructive interference will occur for a film thickness of:
a) L / 8N
b) L / 4N
c) L / 2N
d) 3L / 4N
Ans:
Complete destructive interference will arise for a film thickness of L/2N.