Question

3 A thin film of alcohol is spread over a surface. When light from a tunable source is incident normally, the intensity of reflected light at the detector is maximum for  = 640 nm and minimum for  = 512 nm. Taking the refractive index of alcohol to be 1.36 for both the given wavelengths, the minimum thickness of the film would be __________ nm (Round off to two decimal places).

Answer 1

Answer:

Explanation:

A fine metal foil separates one end of two pieces of optically flat glass. When light of wavelength 500nm is incident normally, 28 dark lines are observed (with one at each end). How thick is the foil? (answer = 6.75um)

A thin film of alcohol (n=1.36) lies on a flat glass plate (n=1.51). When monochromatic light, whose wavelength can be changed, is incident normayll, the reflected light is a minimum for wavelength = 512nm, and wavelength = 640nm. What is the thickness of the film? (answer = 471nm)