Question

ua,ub uc
are refractive indices of media A. B and C respectively, so that ua>ub>uc
The critical angle arises when a ray of light travels from
а)C to A. b)C to B
c)B to A
d)A to c​

Answer 1

The critical angle arises when a ray of light travels from d) a to c​.

Explanation:

On applying Snell's law, we get,

μb/μa = sin C

Where,

μb = Refractive index of denser medium

μa = Refractive index of rarer medium

C = Critical angle

Now, from question, μa > μb > μc which means

Refractive index of 'a' is greatest which is the speed of the light is slowest in medium 'a'. Thus, the medium 'a' is densest medium.

Similarly, the medium 'c' is rarest medium.

The critical angle occurs when the light travels from denser medium to rarer medium.

Thus, the light travels from medium 'a' (denser) to 'c' (rarer).