# Homework Help: Yr 11 question, trouble drawing diagram. Light.

1. Feb 5, 2008

### theperthvan

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

A film director films a scene by photographing it in a plane mirror. The distance from the camera to the actor is 12.0m. The perpendicular distance from the camera to the plane of the mirror is 8.0m. The perpendicular distance from the actor to the plane mirror is also 8.9m. At what distance should the photographer focus her camera

2. Relevant equations

basic, DIAGRAM NEEDED!!

3. The attempt at a solution

no idea

2. Feb 5, 2008

### HallsofIvy

It's hard to believe you are serious- you can't draw? Draw a long line segment representing the mirror. Mark a point representing the camera and draw a perpendicular from it to the line segment. Label that "8.0 m" Draw another mark representing the actor and draw a perpendicular from it to the mirror. Label that "8.9 m". (Was that a typo? You say "also". Did you mean to say "also 8.0 m"?). Draw a line from the camera to the actor and label it "12.0 m". Finally, draw the "light ray" from the actor to the mirror to the camera. That is, one line from the actor to the mirror and another from that point on the mirror to the camera. Remember that the angles the two lines make with the mirror must be equal. The total length of those two lines is the distance the camera must be focused for.

The general problem, which you would have if the two perpendicular distance were really 8.0 m and 8.9 m is an exercise in trigonometry. If the two distances are really equal, both 8.0 m, then it is a relatively simple problem in symmetry.