Two plane wavefronts of light, one incident on a thin convex lens and another on the refracting face of a thin prism. After refraction at them, the emerging wavefronts respectively become

A wave front is an imaginary surface where

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