Using the Huygens' principle, briefly describe reflection of a plane wavefront from a reflecting surface. Hence, prove the laws of reflection.

Consider a plane wave AB incident at an angle i on a reflecting surface MN. v represents the speed of the wave in the medium and $\displaystyle \tau$ represents the time taken by the wavefront to advance from point B to C. $\displaystyle B C=v \tau$ To construct the reflected wavefront, a sphere of radius $\displaystyle v \tau$ from point A is drawn. $\displaystyle A E=B C=v \tau$ Also $\displaystyle \triangle E A C \cong \triangle B A C$ $\displaystyle \therefore i=r$