$A$ well-cut diamond appears bright because

For a light ray to undergo total internal reflection ($i =$ angle of incidence,$i_c =$ critical angle):

Explain the phenomenon of total internal reflection in a right-angled prism.

The wavelength of light in two liquids $x$ and $y$ is $3500 \ \mathring{A}$ and $7000 \ \mathring{A}$ respectively. The critical angle of $x$ relative to $y$ will be.......$^o$

It is found that all electromagnetic signals sent from $A$ towards $B$ reach point $C$. The speed of electromagnetic signals in glass can not be

Three rays of light,namely red $(R)$,green $(G)$ and blue $(B)$ are incident on the face $PQ$ of a right-angled prism $PQR$ as shown in the figure. The refractive indices of the material of the prism for red,green and blue wavelengths are $1.27$,$1.42$ and $1.49$ respectively. The colour of the ray$(s)$ emerging out of the face $PR$ is: