A plane wavefront after being incident on a plane reflector at an angle of incidence `i` , reflects from it. Show that the incident wavefront and the reflected wavefront are inclined at an angle (`180^(@)`-2i) with each other.

Explanation

AB and CD are the incident and reflected wavefronts respectively (Fig .6.9]. On extending the wavefronts , they meet at E and the angle between them is `theta`. From figure `angle`BAC= `i`and `angle`DCA=r. From `Delta` ACE, `theta + i` +r = `180^(@)`
or `theta = 180 ^(@)` -(i+r) or , `theta =180 ^(@)` -2i [`:.` i=r]