The idea of secondary wavelets for the propagation of a wave was first given by
Newton
Huygen
Maxwell
Fresnel
Explain the reflection of plane wavefront from concave mirror.
The figure shows a surface $XY$ separating two transparent media, medium - $1$ and medium- $2$. The lines $ab$ and $cd$ represent wavefronts of a light wave traveling in medium- $1$ and incident on $XY$. The lines $ef$ and $gh$ represent wavefronts of the light wave in medium- $2$ after refraction.
The phases of the light wave at $c, d, e$ and $f$ are $\phi_c,\phi_d, \phi_e$ and $\phi_f$ respectively. It is given that $\phi_c \neq \phi_f.$
Derive the laws of refraction from the concept (Huygen's principle) of the wavefront.
Wavefront of a wave has direction with wave motion