00:01
For this problem on the topic of ray optics, we are told that the reflecting surfaces of two intersecting flat mirrors as shown in the diagram are an angle theta, where theta is between 0 and 90 degrees.
00:13
Now, for a light ray that strikes the horizontal mirror, we want to show that the emerging ray will intersect the incident ray at an angle beta, where beta is 180 degrees minus 2 theta.
00:26
So if we look at our diagram, we can show the path of the light ray, and show that alpha and gamma are the angles of incidence of minerals 1 and 2 respectively.
00:40
Now, using some geometry, let's look at triangle a, b, c, a.
00:47
In this triangle, we can see that 2 alpha plus 2 gamma plus beta must equal to 180 degrees by the angles in a triangle.
01:01
And so if we rearrange this equation, we find that beta must equal to 180 degrees minus 2 into alpha plus gamma...