A lens of refractive index $$\mu$$ is put in a liquid of refractive index $$\mu^{\prime}$$. If the focal length of lens in air is $$f$$, then its focal length in liquid will be

In the given figure, the angle of reflection is

A thin prism $$P_1$$ of angle $$4^{\circ}$$ and refractive index 1.54 is combined with another prism $$P_2$$ of refractive index 1.72 produce dispersion without deviation, the angle of $$P_2$$ is

A simple telescope, consisting of an objective of focal length $$60 \mathrm{~cm}$$ and a single eye lens of focal length $$5 \mathrm{~cm}$$ is focused on a distant object in such a way that parallel rays emerge from the eye lens. If the object subtends an angle of $$2^{\circ}$$ at the objective, the angular width of the image is