The Mirror Equation
We will now transform the geometric drawings into algebraic equations: !! we want to relate s, s’ and R !!
For q a small angle we can approximate:
Plugging these back into the above equation relating the angles, we get:
Defining the focal length f = R/2,
This eqn is known as the mirror eqn. Note that there is no mention of q in this equation. Therefore, eqn works for all small q, ie we have an image!