Visible light of wavelength 520 nm in air strikes a thin plastic film (n = 1.30) that…
PHYSICS · Single correct · A Level · Physics · Waves · Waves
Problem
Visible light of wavelength 520 nm in air strikes a thin plastic film (n = 1.30) that coats glass (n = 1.50). Both the reflection at the air–film interface and the reflection at the film–glass interface undergo a 180° phase change. What is the minimum non-zero film thickness that produces maximum reflected intensity at this wavelength?
(a) 260nm
(b) 100nm
(c) 200nm
(d) 173nm