Light travels with velocity 1.5 x 10^8 m/s in medium 1 and 0.75 x 10^8 m/s in medium 2. What is the refractive index of medium 2 with respect to medium 1?

1. The refractive index of medium 2 with respect to medium 1 is $^1n_2 = \dfrac{v_1}{v_2}$. 2. Substitute: $^1n_2 = \dfrac{1.5 \times 10^8}{0.75 \times 10^8}$. 3. Compute: $^1n_2 = 2$. 4. The value 0.5 is $v_2/v_1$, the index of medium 1 with respect to medium 2, so it is the wrong direction. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 6 "Refraction of Light", p.88_