Define the term wavefront. Using Huygen's wave theory, verigy the law of reflection.

Explanation

Wave front : Wave front is the continuous locus of all such particles of the medum which are vibrating in the same phse.
Laws of reflection on the basis of Huygne's wave theory : Let XY be the reflecting surface and AB is the incident wave and A'B' be the reflected wave front.
Let, v be the speed of light
Time taken by the light to go from point B to B' is equal to the fo from A to A'.
Hence, BB'= AA' (common)
`/_AB B'=/_A A'B("each "90^(@))`
`DeltaABB'=DeltaB'A'A(R.H.S)`
Hence, ` /_BAB'=DeltaA'B'A(C.P.C.T.)`
`/_i=/_r`

Hence, angle of incidence = angle of reflection.