need help

[rossi02]

please help me with this problem.

two plane mirrors are facing each other. They are parallel, 3.00 cm apart, and 17.0 cm in length. A laser beam is directed at the top mirror from the left edge of the bottome mirror. what is the smallest angle of incidence with respect to the top mirror, such that the laser beam (a) hits only one of the mirrors and (b) hits each mirror only once?

[Doc Al]

I assume you know the law of reflection: that the angle of reflection equals the angle of incidence.

So... Where would you have to aim the beam so that the reflected beam just hits the right edge of the bottom mirror? What angle is that? Now consider what happens if you decrease or increase the angle of the beam.

(Draw yourself a picture.)