If $r$ and $r^1$ denotes the angles inside the prism having angle of prism $50^{\circ}$ considering that during interval of time from $t=0$ to $t=t, r$ varies with time as $r=10^{\circ}+t^2$. During the time $r^1$ will vary with time as

In determining the refractive index of a glass slab using a travelling microscope, the following readings are tabulated

(a) Reading of travelling microscope for ink mark $=5.123 \mathrm{~cm}$

(b) Reading of travelling microscope for ink mark through glass slab $=6.123 \mathrm{~cm}$

(c) Reading of travelling microscope for chalk dust on glass slab $=8.123 \mathrm{~cm}$

From the data, the refractive index of a glass slab is

The final image formed by an astronomical telescope is

If the angle of minimum deviation is equal to angle of a prism for an equilateral prism, then the speed of light inside the prism is