00:01
Shown here is the given figure from the problem.
00:05
We know that total internal reflection occurs when the incident angle is greater than the critical angle.
00:20
As such, this problem wants us to determine for the cases where the total internal reflection occurs, either from the top or the bottom layer, determine the amount in which the incident angle exceeds the critical angle.
00:33
So, also, they are occurs.
00:36
Because light travels from a material with a higher index of refraction to a material to smaller index of refraction.
00:59
Thus, in this case, tir is possible when the material above a layer has, above or below the layer, has smaller index of fraction than the layer itself.
01:33
So to solve the problem, we must determine in which cases they are occurs.
01:41
So let's determine that first.
01:46
So for a, for the top, as you can see, above is air, which is less than the index of refraction of layer a.
01:57
So check since air as a less than index fraction than a, which is 1 .3.
02:06
For the bottom, we have an index of fraction of 1 .5, which is 1 .5.
02:11
Which is greater than a.
02:14
So total interreflection does not occur here.
02:17
Now for b, from the top, the top above it is 1 .3, which is smaller than 1 .5.
02:27
So check.
02:28
And for the bottom, we have 1 .4, which is also smaller than 1 .5.
02:33
So check.
02:34
And for layer, the above layer as in this fraction of 1 .5, which is greater than 1 .4...