# Mirror reflection question

1. Feb 20, 2008

### physucsc11

1. The problem statement, all variables and given/known data

A short thin object (like a short length of wire) of length L is placed along the axis of a spherical mirror (perpendicular to the glass surface). Show that its image has length L' = (m^2)*L
so the longitudinal magnification is equal to -m^2 where m is the normal "lateral" magnification. Why the minus sign? (Hint: Find the image positions of both ends of the wire, and assume L is very small.)

2. Relevant equations

$$\frac{1}{d_{i}}$$ = $$\frac{1}{f}$$ - $$\frac{1}{d_{0}}$$

m = - $$\frac{d_{i}}{d_{0}}$$

3. The attempt at a solution

I'm kind of stuck. I was trying to draw ray diagrams but it doesn't make sense how to draw them for an object that is a wire, that is, is very thin. It would be nice if somebody could just give me helpful advice how to approach the problem.