Question

Information in a compact disc is stored in "pits" whose depth is essentially 1/4 the wavelength of the laser light used to "read" the information. That wavelength is 780 nm in vacuum, but the wavelength on which the pit depth is based is measured in the n = 1.55 plastic that makes up most of the disc. Find the pit depth.

Answer 1

The wavelength in vacuum

The wavelength in the plastic is

It is given that the pit depth is based on the wavelength of the laser light in the plastic. Pit depth is 1/4 of the wavelength of the laser light in plastic