00:01
So we have a lake and that lake is full of water.
00:07
The refractive index of water is 1 .333.
00:12
And the lake is 2 .2 meters deep.
00:16
So then light coming up from this point at some critical angle, this light will not be refracted.
00:25
This will become parallel to the surface.
00:29
So what we're trying to figure out here is what is this angle theta c.
00:33
So, sign of theta c is equal to refractive index of air divided by the refractive index of water, and the refractive index of air is equal to 1.
00:46
Refractive index of water is 1 .333.
00:50
So, theta critical, the critical angle, is equal to sine inverse of 1 over 1 .333, and that is equal to 48 .6 degrees...