Question

Does critical angle depend on the colour of light? Explain.

Answer 1

Yes, Colour depends on the wavelength of light, refractive index depends on wavelengths of light. So, far lights of different colours the refractive index changes this implies that critical angle also changes.

The observer can see through distance $P^1{Q}^1$, where reflected ray from $B$ can meet line.

From geometry $CD=d=C^1{P}^1$

$P^1{Q}^1=C^1{D}^1+P^1{D}^1+Q^1{C}^1$

$=d+2PD+2CQ$

$=d+2(PD+9C)$

$=d+2d$

$=3d$