CBSE NOTES CLASS 12 PHYSICS
CHAPTER 10 WAVE OPTICS
Reflection of a plane wave by a plane surface
Consider a plane wave front AB incident at an angle i on a reflecting surface MN. If v represents the speed of the wave in the medium, τ represents the time taken by the wave front to advance from the point B to C then the distance BC = vτ
Let CE represent the new wave front. Now AE = BC = vτ
Triangles EAC and BAC are congruent and therefore, the angles i and r would be equal. This is the law of reflection.