Since Mr. T wasn't here today, I felt that it would be a good idea to talk about all the random light stuff we covered today.
Reflection.
When light tries to enter a new medium at an angle, a portion of the wave's energy is reflected back into the original medium.
The angle that the original ray makes with the normal line is known as the angle of incidence, and the angle that the reflected ray makes with the normal line is the angle of reflection. The most important thing to remember about reflection is that the angle of incidence ALWAYS equals the angle of reflection.
Refraction
Right, so we know that when a wave reaches a new medium, part of the wave's energy just bounces back. What happens to the other part of the light's energy? The remainder of the energy continues on into the new medium, but guess what?
Waves BEND! When light moves from one medium to another, its speed changes, which changes the direction of the wave's travel. This is called refraction.
Note: When objects go from a less "optically dense" medium (i.e. air) to a more "optically dense" medium (water), they bend toward the normal line, but when objects go from a more "optically dense" medium to a less "optically dense" (ex water to air) medium, they bend away from it.
Equations to know and use:
Total internal reflection occurs when none of the light is refracted into the new medium, and all of it is reflected back into the original medium (hence the name). The smallest angle of incidence between 0 and 90 degrees at which this can occur occurs when the angle of refraction = 90 degrees.
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