Question

State Huygens principle. Using it draw a diagram showing the details of passage of a plane wave from a denser into a rarer medium.

Assertion (A) : The phase difference between any two points on a wavefront is zero. Reason (R) : All points on a wavefront are at the same distance from the source and thus oscillate in the same phase.

State Huygens' principle. How did Huygens explain the absence of the backwave ?

Use Huygens' principle to show reflection/refraction of a plane wave by (i) concave mirror, and (ii) a convex lens.