$A$ parallel beam of light strikes a piece of transparent glass having a cross-section as shown in the figure below. The correct shape of the emergent wavefront will be (figures are schematic and not drawn to scale)-

Huygens' principle is applicable to

Assertion $A$: For light diverging from a point source,the intensity at the wavefront does not depend on the distance.
Reason $R$: In a diverging beam of light from a point source,a spherical wavefront is observed.

State and explain Huygens' principle.

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.

Consider a point at the focal point of a convergent lens. Another convergent lens of short focal length is placed on the other side. What is the nature of the wavefronts emerging from the final image?