Manufacturers apply a single-layer magnesium fluoride coating (nc=1.38) to the glass (ng=1.52) elements of a camera lens in order to reduce reflections of green light of wavelength λ0=550 nm in air. The coating is deposited uniformly and the lens is used under normal incidence.
(a) For the two relevant reflections that combine to produce the observed interference, indicate whether each undergoes a half-wavelength phase reversal upon reflection. Justify your answers.
(b) Determine the least non-zero coating thickness that will minimize the reflected intensity of the green light. Show all reasoning and include appropriate units in your answer.
(c) Briefly explain why coatings that minimize reflection often have a thickness that is approximately a quarter of a wavelength within the coating material.