# Homework Help: Concave Mirror Lens Ray Diagram

1. Mar 10, 2008

### petern

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

A person 1.62 m tall wants to be able to see her full image in a plane.
a) What must be the minimum height of the mirror?
b) How far above the floor should it be placed, assuming that the top of the person's head is 15 cm above her eye level? Draw a ray diagram.

2. Relevant equations

None required....

3. The attempt at a solution

I did 1.62 / 2 but that's too easy to be right. I know the ray diagram would be a concave mirror though.

2. Mar 10, 2008

### mgb_phys

The question states a plane (ie flat) mirror.
All you need to know is that the light reflects from the mirror at the same angle to the normal that it arrived.
You have two limiting rays, one from the eyes to the top of the head, and one from the eyes to the feet.
Sketch the diagram and start playing with similair triangles.

3. Mar 10, 2008

### petern

I'm assuming I need to use angles but I really can't tell what is is from the sketch.