Light travels in two media $M_{1}$ and $M_{2}$ with speeds $1.5 \times 10^{8} \text{ m/s}$ and $2.0 \times 10^{8} \text{ m/s}$ respectively. The critical angle between them is.

$A$ light ray falls on a square glass slab as shown in the diagram. The index of refraction of the glass,if total internal reflection is to occur at the vertical face,is equal to

Assertion $(A)$: Propagation of light through an optical fibre is due to total internal reflection taking place at the core-clad interface.
Reason $(R)$: Refractive index of the material of the core of the optical fibre is greater than that of air.

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:

$A$ beam of light consisting of red,green and blue colours is incident on a right-angled prism. The refractive index of the material of the prism for the above red,green and blue wavelengths are $1.39, 1.44$ and $1.47$ respectively.
The prism will

In an optical fibre, the core and cladding are made with materials of refractive indices $1.5$ and $1.414$ respectively. To observe total internal reflection, what will be the range of the incident angle with the axis of the optical fibre?