Write Huygen's principle and principle basically composited ?
In the adjacent diagram,$ CP$ represents a wavefront and $AO$ & $BP$, the corresponding two rays. Find the condition on $\theta$ for constructive interference at $P$ between the ray $BP$ and reflected ray $OP$
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 $\phi_c \neq \phi_f.$
The idea of secondary wavelets for the propagation of a wave was first given by
Huygen's conception of secondary waves
Explain how to get a new wavefront in time $\pi $ using Huygen's principle for plane wavefront.