Physics Paper 2

State the laws of refraction

Answer explanation

The laws of refraction are: 1. The incident ray, the refracted ray, and the normal to the interface all lie in the same plane. 2. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for a given pair of medium

Answer explanation

The effective focal length for two thin lenses in contact is derived using the lens formula and the lens maker's formula to account for the separation distance x.

An equi-convex lens is placed on horizontal plane mirror and pin held vertically above the lens is found to coincide with it's image at 20cm above the lens. When few drops of the liquid are placed between the lens and mirror, the pin has to be raised 10cm to obtain coincidence with the image. If the refractive index of the convex lens is 1.5, find the refractive index of the liquid.

Answer explanation

The refractive index of the liquid is 1.33.

Describe an experiment to determine the refractive index of liquid using air cell.

Answer explanation

Fill a glass cell with the liquid, place it between two air cells, observe the shift in the position of the crosswire when viewed through a microscope. Calculate refractive index using the formula.

Explain with aid of diagram why a thick plane mirror forms multiple image

Answer explanation

A thick plane mirror forms multiple images due to the reflection of light rays from different layers of the mirror. Each layer reflects light, creating multiple images.

Explain why glass prisms are preferred to plane mirrors in optical instruments.

Answer explanation

Glass prisms are preferred to plane mirrors in optical instruments because prisms can refract light, leading to less light loss compared to mirrors which only reflect light.

A monochromatic light is incident at an angle of 450 on a glass prism of refracting angle 700 in air. The emergent light grazes the other refracting surface of the prism. Find the refractive index of the glass material.

Answer explanation

The refractive index of the glass material can be calculated using Snell's Law. By applying Snell's Law at the first surface and then at the second surface, the refractive index of the glass material is found to be 1.5.

What is angular magnification

Answer explanation

Angular magnification is the ratio of the apparent size of an object as seen through a lens to the actual size of the object. It is a measure of how much larger or smaller an object appears when viewed through a lens.

Derive the expression for magnification of compound microscope in normal adjustment

Answer explanation

The magnification of a compound microscope in normal adjustment is given by the product of the magnification of the objective lens and the eyepiece lens.

Why should the objective and eye piece of compound microscope have short focal length?

Answer explanation

To minimize aberrations and increase magnification. Short focal lengths allow for a wider field of view and better resolution.