The refraction of light ray takes place from air to water, water to glass and again
glass to air. The ray emerges parallel to incident ray. The correct relation is
\(\left[\mathrm{n}_{\mathrm{a}}, \mathrm{n}_{\mathrm{w}}, \mathrm{n}_{\mathrm{g}}\right.\) represent refractive indices of air, water and glass respectively.

1. A \(\mathrm{g}^{\mathrm{n}}_{\mathrm{w}}=\frac{\mathrm{a}^{\mathrm{n}} \mathrm{g}}{\mathrm{a}^{\mathrm{n}} \mathrm{w}}\)
2. B \(\mathrm{g}^{\mathrm{n}} \mathrm{w}=\mathrm{a}^{\mathrm{n}} \mathrm{g} \times \mathrm{a}^{\mathrm{n}} \mathrm{w}\)
3. C \(\mathrm{w}^{\mathrm{n}} \mathrm{g}=\frac{\mathrm{a}^{\mathrm{n}} \mathrm{w}}{\mathrm{a}^{\mathrm{n}} \mathrm{g}}\)
4. D \(\mathrm{w}^{\mathrm{n}} \mathrm{g}=\frac{\mathrm{a}^{\mathrm{n}} \mathrm{g}}{\mathrm{a}^{\mathrm{n}} \mathrm{w}}\)