Define the term wavefront. Using Huygens' wave theory, verify the laws of reflection.

Explanation

Let XY be an plane reflecting surface and AMB, the incident plane wavefront. All the particles on AB will be vibrating in phase. Let i be the angle of incidence and r the angle of reflection. In the time the disturbance at A reaches C, the secondary waves from the point B must travel a distance BD equal to AC. With the point B as centre and radius equal to AC a sphere is constructed.
From the point C, we draw tangents CD and CD.. Then, BD= BD.
In `DeltaBAC and DeltaBDC`, BC is common, BD= AC and `angleBAC= angleBDC= 90^(@)`
`therefore DeltaBAC= DeltaBDC`
and `angleABC= angleBCD`
But `angleABC=i and angleBCD=r`, i.e., i=r or the angle of incidence is equal to the angle of reflection