A uniform thin film of oil of refractive index n = 1.45 is floating on water of refractive index nw = 1.33. White light is incident from the air above at angle of incidence of 30 degrees, and partly reflected from the air-oil and oil-water interfaces, and interference occurs; the reflected light is analysed with a spectrometer measuring intensity vs wavelength. It is observed that the reflected intensity has a maximum at wavelength 560 nm, and the next intensity minimum is at 630 nm. Calculate the thickness of the oil film.

A uniform thin film of oil of refractive index n = 1.45 is floating on water of refractive index nw = 1.33. White light is incident from the air above at angle of incidence of 30 degrees, and partly reflected from the air-oil and oil-water interfaces, and interference occurs; the reflected light is analysed with a spectrometer measuring intensity vs wavelength. It is observed that the reflected intensity has a maximum at wavelength 560 nm, and the next intensity minimum is at 630 nm. Calculate the thickness of the oil film.