00:01
So we're told that there's a pool, right? and this is the surface of the pool.
00:08
And this is the bottom of the pool.
00:11
So we have some light fixture that's right here and it's emitting some light.
00:15
It is forming a circle on the surface.
00:19
So at these surfaces, we can assume that total internal reflection is occurring.
00:27
Because there's a ring of, if you think about the pool, right, and there's a ring appearing from the bottom, that means that the light is not transmitting at these points.
00:39
It is being completely reflected inside, and that's what you're seeing as a ring.
00:44
So if that reflection is occurring at these points, that means that we can use our good old equation, sine of theta c is equal to n2 over n1.
00:57
So since n2 is simply the medium, that's one, the air medium, that is one, and n1 we can look up in the table is 1 .33.
01:10
So the critical angle is going to be the inverse sign of 1 over 1 .33, and that gives us an angle of 48 .6 degrees...