00:01
In this question, we are given three materials, one, two, and three, and then light travels from material one into material two, and then the light ray that is incident, and into material two, and then the light ray that is incident at the interface between two and three is at the critical angle.
00:18
Okay, so total internal reflection takes place.
00:20
We are given that n1 is 1 .70 and 2 is 1 .60.
00:32
The critical, not critical angle, but 5 is 60 degrees.
00:40
So we want to find entry and get data and what happens when data is decreased.
00:48
So to do part a, which is to find the angle or the refractive index of material 3 so we'll be using snail's law okay for the interface between material materials 2 and 3 okay so from the diagram before that okay i need to write down snow slough which says n2 x theta c is equal to n3 sine 90 degrees okay and then so sign data c so n3 is equal to n2 sine data c from diagram okay data c is equal to five which is 60 degrees okay so n3 equals to n2 sine 60 degrees 1 .6 sine 60 degrees is, okay, the answer is 1 .39.
02:33
Okay, so this is the answer for part a.
02:38
Then we need to find angle data.
02:46
So we need this angle, this angle is 30 degrees, when 5, 60 degrees...