In the adjoining diagram, a wavefront $AB$, moving in air is incident on a plane glass surface $XY$. Its position $CD$ after refraction through a glass slab is shown also along with the normals drawn at $A$ and $D$. The refractive index of glass with respect to air ($\mu = 1$) will be equal to
$\frac{{\sin \theta }}{{\sin \theta '}}$
$\frac{{\sin \theta }}{{\sin \phi '}}$
$\frac{{\sin \phi '}}{{\sin \theta }}$
$\frac{{AB}}{{CD}}$
Figure shown plane waves refracted for air to water using Huygen's principle $a, b, c, d, e$ are lengths on the diagram. The refractive index of water wrt air is the ratio.
What is visible light ? Write various view on it.
What is the shape of the wavefront in each of the following cases:
$(a)$ Light diverging from a point source.
$(b)$ Light emerging out of a convex lens when a point source is placed at its focus.
$(c)$ The portion of the wavefront of light from a distant star intercepted by the Earth.
Explain the reflection of a plane wave using Huygen's principle.
Huygen’s principle of secondary wavelets may be used to