a) Use Huygen’s geometrical construction to show how a plane wave-front at t = 0 propagates and produces a wave-front at a later time. (b) Verify, using Huygen’s principle, Snell’s law of refraction of a plane wave propagating from a denser to a rarer medium. (c) When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency. Explain why.

a) Use Huygen’s geometrical construction to show how a plane wave-front at t = 0 propagates and produces a wave-front at a later time. (b) Verify, using Huygen’s principle, Snell’s law of refraction of a plane wave propagating from a denser to a rarer medium. (c) When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency. Explain why.