Light emerges out of a convex lens when a source of light kept at its focus. The shape of wavefront of the light is:

Newton postulated his corpuscular theory on the basis of

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.

A plane wavefront travelling in a straight line in vacuum encounters a medium of refractive index $\mu$. At $P,$ the shape of the wavefront is :

Carefully analyses the diagram and choose the correct option :