Carefully analyses the diagram and choose the correct option :
$i$ and $ii$ are true
$i$ and $iii$ are true
$i$ and $iv$ are true
$ii$ and $ii$ are true
Huygen's theory of secondary waves can be used of find
The wavefront of a distant source of unknown shape is approximately
Derive the laws of refraction from the concept (Huygen's principle) of the wavefront.
Explain how to get a new wavefront in time $\pi $ using Huygen's principle for plane wavefront.
A parallel beam of light strikes a piece of transparent glass having cross section as shown in the figure below. Correct shape of the emergent wavefront will be (figures are schematic and not drawn to scale)-