00:01
We're asked to find a critical angle for a liquid when the angle of incident is 30 degrees and the angle of refraction is 22 degrees when it's coming from air into that liquid.
00:12
So n -sub -1 is 1, theta -1 is 30 degrees, and theta -2 is 22 degrees.
00:17
And we're asked to find the critical angle, or theta -c.
00:21
Well, the sign of the critical angle is just going to be equal to the ratio of the first medium to the second medium.
00:31
But we need to know the index of refraction of the second medium, n sub 2.
00:36
So to do that, we can go back to snell's law, which says the sine of theta 1, multiplied by the index of refraction of 1, so n sub 1, is equal to the index refraction 2 times the sign theta 2.
00:55
Ok, well, we know theta 1, theta 2, and n sub 1...