Light waves propagate rectilinearly due to:

Select the correct option regarding the history and nature of light.

Explain the refraction of a plane wavefront by a thin convex lens.

The wave theory of light was given by

The following figure represents a wave front $AB$ which passes from air to another transparent medium and produces a new wave front $CD$ after refraction. The refractive index of the medium is $:$ ($PQ$ is the boundary between air and the medium)

What is the shape of the wavefront of light diverging from a point source?