16. • A film on a lens with an index of refraction of 1.5 is 1.0 × 10−7 m is thick and is illuminated with white light. The index of refraction of the film is 1.4.

(a) The number of waves that experience the 180° phase shift is (1) zero, (2) one, (3) two. Explain.

(b) For what wavelength of visible light will the lens be nonreflecting?