Answer:

The value of refractive index of a medium, when the critical angle is given, can be found out by the formula:

Here, n refers to the refractive index and refers to the critical angle.

According to the question, = 30°. Hence substituting in the formula we get:

Hence the refractive index is 2.

We know that.

Where c is the speed of light and v is the speed of light in the medium.

Substituting the known values we get:

Hence the speed of light in that medium is 1.5 × 10⁸ m/s.