A thin soap film (n = 1.33) suspended in air has a uniform thickness. When white light strikes the film at normal incidence, violet light (λV = 420 nm) is constructively reflected.
(a) If we would like green light (λG = 560 nm) to be constructively reflected, instead, should the film's thickness be increased or decreased?
(b) Find the new thickness of the film. (Assume the film has the minimum thickness that can produce these reflections.)