Which of the following is the correct statement?

The ray of light:

Figure shows plane waves refracted from air to water using Huygens' principle and $a$, $b$, $c$, $d$, $e$ are lengths on the diagram. The refractive index of water with respect to air is in the ratio

In the adjoining diagram, a wavefront $\mathrm{AB}$ is moving in the air, is incident on a plane glass surface $\mathrm{XY}$, its position $\mathrm{CD}$ after refraction through a glass slab is shown along the normals drawn at  $\mathrm{A} \mathrm{and} \mathrm{D}$.

The refractive index of the glass w.r.t air ${}_{\mathrm{g}}{}^{\mathrm{a}}\mathrm{\mu }$ will be equal to:

Statement (S): Using Huygen's eye-piece measurements can be taken but are not correct.

Reason (R): The cross wires, scale and final image are not magnified proportionately because the image of the objects is magnified by two lenses, whereas the cross wire scale is magnified by one lens only.

Identify the correct one

The adjoining figure represents a wavefront $\mathrm{AB}$ which passes from air to another transparent medium and produces a new wavefront $\mathrm{CD}$ after refraction.

The refractive index of the medium is ($\mathrm{PQ}$ is the boundary between air and the medium)