Huygens’ principle — UPSC CSE 2023 Physics PYQ

Using Huygens' principle for a plane wave travelling from rarer medium 1 to a denser medium 2, show that \frac{\sin i}{\sin r} = \frac{v_1}{v_2} = \frac{\mu_2}{\mu_1}, where i and r are the angles of incidence and refraction, respectively. v_1, \mu_1 and v_2, \mu_2 are the velocities and refractive indices in media 1 and 2, respectively.