What is the thinnest soap film (excluding the case of zero thickness) that appears black when illuminated with light with a wavelength of 535 nm ? the index of refraction of the film is 1.33, and there is air on both sides of the film.

Explanation:

It is given that,

The thinnest soap film appears black when illuminated with light with a wavelength of 535 nm,

Refractive index,

We need to find the thickness of soap film. The soap film appear black means there is an destructive interference. The condition for destructive interference is given by :

t = thickness of film

m = 0,1,2....

= refractive index

For thinnest thickness, m = 1

Hence, this is the required solution.