# Homework Help: Need help on Plane Mirror

1. Dec 6, 2009

### vu95112

Plane Mirror
A person walks into a room that has, on opposite walls, two plane mirrors producing multiple images. Find the distances from the person to the first three images seen in the left-hand mirror when the person is 5ft from the mirror on the left wall and 10 ft from the mirror on the right wall.

I know the first image is 10 ft because in the plane mirror, the image is as far behind the mirror as the object is in front. I donâ€™t know how to figure out the second and the third images? I need you help please. Thank you.

Vu95112

2. Dec 6, 2009

### denverdoc

Try making a diagram like that found in scrolling down the page at http://dev.physicslab.org/Document.aspx?doctype=3&filename=GeometricOptics_PlaneMirrors.xml":

It may help to keep you from getting confused. The first image in the left mirror is the virtual image of the person and as you say 10' behind the mirror. Apply the same logic to the first image in the right mirror. It would be 5' behind the mirror and since the mirrors are 15' apart, would seem to be 20' away. And so forth.

Last edited by a moderator: Apr 24, 2017
3. Dec 6, 2009

### vu95112

Hello denverdoc,
Thank you very much for your help. A diagram is very useful.
The first image is 10ft
The second image is 30 ft
The third image is 40 ft

Thank you,

Vu95112

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