If P is a vacuum and pnq = 2.6, then:

Correct answer: a The speed of light is greater in p

P is a vacuum, so n(p) = 1. pnq = 2.6 means the index of q with respect to p is 2.6 = v(p)/v(q), so v(p) = 2.6 × v(q). The speed is greater in p.

Why the other options are wrong

• b q is the rarer medium: Here q has n = 2.6 > 1, and the medium with the larger n is the denser one. So q is denser, not rarer.
• c The speed of light is greater in q: The other way round. v(p)/v(q) = 2.6 > 1 means the speed in q is smaller. Light is slower in a denser medium.
• d The angle of incidence and the angle of refraction are equal: The angles would be equal only if the two n were equal. Here n(q) > n(p), so θ2 < θ1: the ray bends toward the normal.