A near sighted person wears eye glass of power 5.5D for distant vision. His doctor prescribes a correction of + ID in near vision part of his bifocals, which is measured relative to the main part of the lens. Then, the focal length of his near vision part of the lens is

Sunil is a student of class VIII in a public school in Delhi. During summer vacation, his parents planned a visit to Haridwar by their car. During the journey from Delhi to Haridwar, Sunil sat on the front seat and his father was driving the car. Sunil observed that the road ahead on the highway appears to be wet but when the car reached the spot, road is found to be dry. He was perplexed by this observation. He asked his father. His father advised Sunil not to disturb him during driving and said that he will discuss the problem on reaching Haridwar. In the evening, when they were settled in a hotel at Haridwar, Sunil’s father told him that the illusion observed by Sunil was on account of atmospheric refraction. Now, Sunil was happy as he knew the real explanation of his observation.

(i) What is atmospheric refraction?

(ii) Name any two phenomena based on atmospheric refraction

(iii)What characteristic was shown by Sunil during his journey?

(iv) What advice was given by Sunil’s father to him and why?

For a healthy eye, the rays of light entering the eye form a sharp image on retina. For a myopic eye, the rays from distant objects focus in front of the retina forming a blurred image. Which of the following lenses shown below will help to correct myopia?

In given figure, a light ray AB is incident normally on one face PQ of an equilateral glass prism.

Find out the angles at faces PQ and PR.

A thin prism p₁ with angle 4° and made from glass of refractive index 1.54 is combined with another prism p₂ made from glass of refractive index 1.92 to produce dispersion without deviation. Then the angle of prism P₂ is