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 (when, n=1,2,3,…..)`
For minimum thickness `t, n=1 or 2mut=lambda//2`
The minimum thickness of a soap bubble,
`t=lambda/(4mu) = (600)/(4xx1.33)=112.78 nm`