A soap film is 465 nm thick and lies on a glass plate . Sunlight, whose wavelengths (in vacuum) extend from 380 to 750 nm, travels through the air and strikes the film perpendicularly. For which wavelength(s) in this range does destructive interference cause the film to look dark in reflected light?

Explanation:

We can calculate the maximum wavelength in which the thin film presents destructive interference. Below this wavelength, there are no colors reflected, and the thin film looks dark.

The max wavelength is given by the expression:

where m is the order of the interference pattern, n is the refractive index and d is the thin of the film. By replacing we obtain:

below this values no other colors are reflected.

hope this helps!!

the inner core.

good luck: )

klicker