Question

Calculate the minimum thickness of a soap bubble film `(mu=1.33)`that results in constructive interference in the reflected light if the film is illuminated with light whose wavelength in free space is `lambda=600nm`.

Answer 1

For constructive interference in case of soap film,
` 2mut = (n-1/2)lambda` (n=1,2,3………)
For minimum thickness t , n=1
` or 2mut = lambda/2 or t = lambda/4mu = 600/(4 xx 1.33)`
= 112.78 nm .