The critical angle for a typical glass air interface is $42^{\circ}$. If a ray of light falls normally on one of the faces of the prism of angle $45^{\circ}$. The emergent ray will:

The distance between the objective and eye piece of astronomical telescope in normal adjustment is 27 cm and its magnifying power is 8 . What is the focal length of the eye piece?

The ratio of the angle of deviation produced by a thin prism, when it is placed in air to the angle of deviation produced when it is immersed in water of refractive index $\frac{4}{3}$ is:

An object placed 40 cm in front of a thin convex lens is moved to 60 cm from the lens. If the focal length of the lens is 30 cm the ratio of magnification of the image at the initial position to the final position is: