Anti-reflective coatings on lenses use thin-film interference to eliminate the reflection of a particular color. Suppose a glass lens (ng = 1.53) is covered with a thin film (nf = 1.31) to prevent green light (λ = 534 nm) from being reflected.

(a) write an expression for the minimum thickness the film can have, t.
(b) Calculate the minimum thickness, t, in nanometers?