Inside a vessel filled with liquid a converging lens is placed as shown in figure. The lens has focal length $$15 \mathrm{~cm}$$ when in air and has refractive index $$\frac{3}{2}$$. If the liquid has refractive index $$\frac{9}{5}$$, the focal length of lens in liquid is

A ray of light travels from a denser medium to a rarer medium. The reflected and the refracted rays are perpendicular to each other. If '$$r$$' and '$$r_1$$' are the angle of reflection and refraction respectively and '$$\mathrm{C}$$' is the critical angle, then the angle of incidence is

A convex lens of focal length 'F' produces a real image 'n' times the size of the object. The image distance is

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