00:01
All right, so we're going to look at fermat's principle of least time.
00:05
And let's say this is our interface.
00:07
This black line is the interface.
00:08
And the red line is the normal direction relative to the interface.
00:13
And let's say we have light coming in at some incident angle.
00:17
We'll call this theta 1.
00:19
And then it is refracted by some other angle theta 2.
00:23
And we want to minimize the time it takes for the light to travel a certain distance d.
00:28
So let's say that, sorry, let me re -draw that distance a little bit.
00:33
So this distance approximate, let's just call this d.
00:36
And let's call this distance x, and so therefore this distance is d minus x...