C.3.10—Thin-film interference Topic Practice
C.3.10—Thin-film interference Topic Practice
Practise tracking reflected rays in thin films to decide phase reversals and calculate thickness or missing reflected wavelengths.
How this is tested
- identify on a ray diagram which reflection gives a 180° phase change by comparing refractive indices
- use 2nt = mλ, or the quarter-wave form, at normal incidence to find film thickness or a missing wavelength
- explain a missing reflected colour using two reflected rays, phase reversal, and destructive interference