A light beam is moving though the first medium toward the second medium. In order for total internal reflection to be possible, what must be the relationship of the indexes of refraction of the first medium and the second medium

n₁ must be greater than n₂  in order for total internal reflection to be possible.

Explanation:

From Snell's law:

We have that total internal reflection is produced when the angle of refraction is 90°, so the incident angle becomes the critical angle.

Now, the snell's equation will be:

It will be possible just if n₁ > n₂.

Therefore,  the index of refraction of the first medium (n₁) must be greater than the index of refraction of the second medium (n₂) in order for total internal reflection to be possible.

I hope it helps you!

b.a device that inputs heat into a cool object