Question

A soap bubble film (n=1.42) of thickness 106 nm results in a constructive interference in the reflected light if this film is illuminated by a beam of light with a wavelength of 601 nm. What are the next three thicknesses of this film that will also result in a constructive interference?

Answer 1

Constructive interference occurs here when -

2 t_c = $\lambda$_n / 2, 3 ($\lambda$_n / 2), 5 ($\lambda$_n / 2)

we know that, t_c = ($\lambda$_n / 4) = 106 nm

The next three thicknesses of this film which will be given as :

t_c' = 3 (106 nm) = 318 nm

t_c'' = 5 (106 nm) = 530 nm

t_c''' = 7 (106 nm) = 742 nm