List of top Physics Questions on huygens principle

According to Huygen's principle, secondary wavelets move:
Huygen's principle does not use
Spherical wave fronts, emanating from a point source, strike a plane reflecting surface. What will happen to these wave fronts, immediately after reflection ?
A wave has velocity $v$ in medium $P$ and velocity $2v$ in medium $Q$. If the wave is incident in medium $P$ at an angle of $30^{\circ}$, then the angle of refraction will be
Sound waves in air cannot be polarized because
The wave theory of light was given by
A glass slab of thickness 4 cm contains same number of waves as 5 cm thickness of water, when both are traversed by the same monochromatic light. If the refractive index of water is 4/3, what is the refractive index of glass:
The $6563 \,?$ $H_\alpha$ line emitted by hydrogen in a star is found to be red-shifted by $15\,?$. The speed with which the star is receding from the earth is
Sound waves travel fastest in