# Refraction and reflection

1. Mar 15, 2005

### figs

Prove mathematically that when a plane mirror is rotated an angle theta about an axis through its center, the angle of deflection of a light is equal to 2theta. How am i to show draw this out? I have already drawn my points and lined up my angles with and without the mirror rotated. I dont know what direction to take my proof now.

2. Mar 15, 2005

it depends on what you mean by the angle of deflection. Do you mean the angle of incidense + the angle of reflection. If this is the case, rotationg the mirror by an angle $$\theta$$ would increase both the angle of incidence and the angle of reflection by $$\theta$$, resulting in an angle difference of $$2\theta$$.