The phenomenon of total internal reflection is observed when the angle of incidence is

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?

Consider telecommunication through optical fibres. Which of the following statements is not true?

$A$ ray of light is travelling from glass to air. (refractive index of glass $= 1.5$). The angle of incidence is $50^{\circ}$. The deviation of the ray is

The radius of the light circle observed by a fish at a depth of $12 \ m$ is (refractive index of water $\mu = 4/3$):

$A$ ray of light enters from air into a denser medium of refractive index $\mu = \frac{4}{3}$,as shown in the figure. The light ray undergoes total internal reflection at the adjacent surface as shown. The maximum value of angle $\theta$ should be equal to -