A thin uniform film of oil lhal can be varied in thickness c

A thin uniform film of oil lhal can be varied in thickness covers a sheet of glass of refractive index 1.52. The refractive index of the oil is 1.64. Light of wavelength 555 nm is shone from air at normal incidence on the film. Starting with no oil on the glass, you gradually increase the thickness of the oil film until the first interference maximum in the reflected light occurs. What is the thickness of the oil film at that instant?

Solution

Thickness of the film

t= lamda / 4 n

    = ( 555 nm ) / 4 ( 1.65 )

     =84.09 nm