00:01
So we have this prism here, and light enters it parallel to the base.
00:05
And then when it exits the prism, it disperses into a rainbow.
00:10
And we want to calculate the exact angle of emergence of the red light and the blue light.
00:18
And then calculate the dispersion angle, which is just the difference between the two.
00:23
And to do that, we're going to use snell's law.
00:26
But before i do that, i just want to point out a couple of things about this diagram here.
00:31
Like i mentioned earlier, the light enters parallel to the base.
00:35
And since the base here is the 30 degrees, that means this angle here must also be 30 degrees.
00:43
And since i've drawn this here is a right angle, and this angle must be 60.
00:49
And i can use that to calculate alpha.
00:52
And if you'll be this triangle with the red, green, and white line, i have the right angle here and the two angles, alpha, and beta.
01:01
Which means that alpha plus beta must equal 90 degrees.
01:07
Anyway, moving on, you can start with either the red or the blue, but i'm just going to start with the red.
01:15
So the light enters the prism from the air.
01:19
We have one times the sign of 60 degrees equal 1 .307.
01:26
The sign of alpha.
01:29
We're going to solve this for alpha.
01:31
We get alpha equals the arc sine.
01:36
Of 60 degrees divided by 1 .307.
01:44
That's supposed to be a 7.
01:48
And that ends up equaling 41 .5 degrees...