According to corpuscular theory of light, the different colours of light are due to

Figure, shows wave fronts in still water moving in the direction of the arrow towards the interface $PQ$ between a shallow region and a deep(denser) region. Which of the lines shown may represent one of the wave fronts in the deep region?

Consider a point at the focal point of a convergent lens. Another convergent lens of short focal length is placed on the other side. What is the nature of the wavefronts emerging from the final image ?

What is visible light ? Write various view on it. 

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 $\phi_c \neq \phi_f.$