00:01
So we have this plain mirror before and after it's rotated by an angle alpha.
00:06
And we want to show that by rotating the mirror by this amount, this causes the beam to rotate, the reflected beam, to rotate through an angle of 2 alpha.
00:18
So what we're going to do is we're first going to draw the ray, the incident ray and reflected ray on this first mirror.
00:28
So as we can see here, we have some.
00:31
Angle theta that the incident ray forms with the normal axis to the plane mirror.
00:39
And we know that the angle of incidence is equal to the angle of reflection.
00:44
So we know that this angle on the right side as well is going to be equal to theta.
00:50
So if we now consider the scenario where we shift or we tilt the plane mirror by this degree alpha, so we'll have this same ray coming in, theta, and this angle theta is between the incident ray and what was formerly the normal axis...