By Huygen's wave theory of light,we cannot explain the phenomenon of

According to Huygens principle, the phase difference between oscillations of any two particles on the same wave front is . . . . . . rad.

Carefully analyze the given diagrams and choose the correct option regarding the refraction of a plane wavefront by a thin convex lens:

When a plane wave front is incident on a concave mirror as shown in the figure,what is the shape of the reflected wave front?

The speed of light in water is less than the speed of light in air,confirms the assumption of which theory of light?

Derive the laws of refraction using the concept of Huygens' principle of wavefronts.