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

Given below are two statements:
Statement-$I$: $A$ plane wave after passing through a prism remains a plane wave,but passing through a small pinhole may become a spherical wave.
Statement-$II$: The curvature of a spherical wave emerging from a slit will increase for increasing slit width.
In the light of the above statements,choose the correct answer from the options given below.

Describe the short history of light.

The phase difference between any two particles in a given wavefront is . . . . . . rad.

You have learnt in the text how Huygens' principle leads to the laws of reflection and refraction. Use the same principle to deduce directly that a point object placed in front of a plane mirror produces a virtual image whose distance from the mirror is equal to the object distance from the mirror.

Which one of the following phenomena is not explained by Huygen's construction of wavefront?