# Mirrors question

• Apr 30th 2008, 09:19 AM
pvcmd1
Mirrors question
Two people stand 3.0 m away from a large plane mirror and are 5.0 m apart from each other in a dark room. At what angle of incidence should one of them shine a flashlight on the mirror so that the reflected beam strikes the other person at the same height that the flashlight is held? Assume the person with the flashlight holds it near his body?

Completely lost on this. Any help will be greatly appreciated.
• Apr 30th 2008, 12:15 PM
topsquark
Quote:

Originally Posted by pvcmd1
Two people stand 3.0 m away from a large plane mirror and are 5.0 m apart from each other in a dark room. At what angle of incidence should one of them shine a flashlight on the mirror so that the reflected beam strikes the other person at the same height that the flashlight is held? Assume the person with the flashlight holds it near his body?

Completely lost on this. Any help will be greatly appreciated.

Since angle of incidence is equal to angle of reflection, the two angles theta are equal. Thus the two triangles with theta in them are congruent, etc. So the light path splits 5 m along the mirror into equal parts. You can use a little trig to get the rest.

-Dan