There are four convex lenses $$L_1, L_2, L_3$$ and $$L_4$$ of focal length $$2,4,6$$ and 8 cm, respectively. Two of these lenses from a telescope of length 10 cm and magnifying power 4. The objective and eye lenses are respectively

Refractive index of the medium is $$\mu$$ and wavelength is $$\lambda$$, then which of the following proportionality relation is correct?

A ray of light travelling through glass of refractive index $$\sqrt{2}$$ is incident on glass-air boundary at an angle of incidence $$45^{\circ}$$. If refractive index of air is 1 , then the angle of refraction will be $$\left[\sin 45^{\circ}=\frac{1}{\sqrt{2}}, \sin 90^{\circ}=1\right]$$

A ray of light is incident at an angle $$i$$ on one face of prism of small angle $$A$$ and emerges normally from the other surface. $$\mu$$ is the refractive index of the material of the prism. The angle of incidence is