00:01
Okay, this problem is very similar to problem number 14, except that they tell us the angle at which the ray comes out of this optic fiber relative to the surface of the fiber.
00:17
So we're going to work our way backwards to figure out at what angle this ray originated.
00:23
So this here is the angle that is relative to the surface of the fiber.
00:29
And in order to use snell's law, we need to use the reflected ray.
00:34
So this ray and this ray here, i'm sorry, this angle and this angle here make up 90 degrees.
00:42
So angle 1 is 85 degrees.
00:47
And now we're going to use snells law to figure out angle two, the incident angle between these two mediums.
00:55
So we set it up n1, sine theta 1, equal to n2.
01:02
2, sine theta 2, and we plug in the values that are given to us 1 .2, sine theta 2, and then we want to isolate theta 2 in order to solve for it.
01:22
And in order to do that, we need to get this sign away from it.
01:26
So we use the inverse sign 1 .0, sine 85, divided by 1 .2.
01:39
And that gives us an angle of about 56 .1 degrees.
01:46
All right, so now we've got that angle.
01:48
We need to figure out the incident angle here.
02:00
So now we're going to solve for angle three...