In Snell's law of refraction, the refractive index of the second medi…

The correct answer is Option (3) → independent of the angle of incidence.

Snell's law is \( \sin i/\sin r = n_{21} \), where \( n_{21} = n_2/n_1 \) is the relative refractive index of the two media.

Option (1) a characteristic of the medium 1 only — Incorrect. \( n_{21} = n_2/n_1 \) depends on both media, not on medium 1 alone.

Option (2) a characteristic of the medium 2 only — Incorrect. It depends on both media, not on medium 2 alone.

Option (3) independent of the angle of incidence. — Correct. The ratio \( \sin i/\sin r \) is a constant for the two media; it does not change with the angle of incidence.

Option (4) not dependent on the wavelength of light — Incorrect. The refractive index of a medium changes with wavelength, which is why a prism disperses white light, so \( n_{21} \) depends on the wavelength.

NCERT (2026-27):
Refraction – “… We have

    \( \displaystyle \frac{\sin i}{\sin r} = n_{21} \qquad (9.10) \)

where n₂₁ is a constant, called the refractive index of the second medium with respect to the first medium. Equation (9.10) is the well-known Snell’s law of refraction. We note that n₂₁ is a characteristic of the pair of media (and also depends on the wavelength of light), but is independent of the angle of incidence.”