Question: In a thin film of oil on water, if the thickness of the oil film is 0.5 μm and the wavelength of light in air is 600 nm, what is the wavelength of light in the oil?

Options:

1. 400 nm
2. 500 nm
3. 600 nm
4. 700 nm

Correct Answer: 600 nm

Solution:

Wavelength in oil = λ/n, where n is the refractive index of oil. Assuming n = 1.5, λ_oil = 600 nm / 1.5 = 400 nm.