When light is incident on a thin transparent film, the light waves reflected from the front and back surfaces interfere. For near normal incidence, the wavelength condition for maximum intensity of the light reflected from a film in air are:
1
L = mλ/2, where m is an integer, L is its thickness and λ is wavelength of light in air.
2
2L = mλ , where m is an integer, L is its thickness and λ is wavelength of light in air.
3
\(\rm 2L=\left(m+\frac{1}{2}\right)\frac{λ}{n_2}\), Where m is an integer, n2 is the index of refraction, L is its thickness and λ is wavelength of light in air.
4
\(\rm 2L=m\frac{λ}{n_2}\), Where m is an integer, n2 is the index of refraction, L is its thickness and λ is wavelength of light in air.