Question

Discuss the action of prism , a convex lens and a concave mirror, when a plane wavefront is incident on each of them?​

Answer 1

Answer:

(i) Action of the prism when a plane wave front incident on it: In adjacent figure, consider a plane wave passing through a thin prism. Since the speed of light waves is less in glass, the lower portion of the incoming wave front which travels through the greatest thickness of glass will get delayed resulting in a tilt in the emerging plane wave front.                                                       (ii) Action of the convex lens when a plane wave front incident on it: In the adjacent figure, a plane wave incident on a thin convex lens; the central part of the incident plane wave traverses the thickest portion of the lens and is delayed the most. The emerging wave front has a depression at the center and therefore the wave front becomes spherical (radius = f, focal length) and converges to the point focus F.                                                                            (iii) Action of the concave mirror when a plane wave front incident on it: In adjacent figure, a plane wave is incident on a concave mirror and on reflection we have a spherical wave converging to the focus F.

Explanation: