Electromagnetic waves are incident normally on a perfectly reflecting surface having surface area $A$. If $I$ is the intensity of the incident electromagnetic radiation and $c$ is the speed of light in vacuum, the force exerted by the electromagnetic wave on the reflecting surface 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
A luminous point object $O$ is placed at a distance $2 R$ from the spherical boundary separating two transparent media of refractive indices $n_1$ and $n_2$ as shown, where $R$ is the radius of curvature of the spherical surface. If $n_1=\frac{4}{3}, n_2=\frac{3}{2}$ and $R=10 \mathrm{~cm}$, the image is obtained at a distance from $P$ equal to