Refraction Through A Lens

Question 1

Define lens

Answer 1

A lens is a transparent refracting medium bounded by either two spherical surfaces or one spherical surface and the other surface plane

Question 2

How can a plane surface be treated as a spherical surface?

Answer 2

It can be treated as a spherical surface of infinite radius of curvature

Question 3

Name the two kinds of lenses

Answer 3

1. Convex or converging lens

2. Concave or diverging lens

Question 4

Give the appearance of a convex lens

Answer 4

It is thick in its middle and thin in its periphery - it bulges out in the middle

Question 5

What effect does a convex lens have on an incident light beam?

Answer 5

It converges on passing through a convex lens

Question 6

Name the three kinds of convex lens

Answer 6

1. Bi-convex / double convex/ equi-convex
2. Plano-convex
3. Concavo-convex

Question 7

Give the appearance of a bi-convex lens

Answer 7

It has both its surfaces convex

Question 7

Give the appearance of a bi-convex lens

Answer 7

It has both its surfaces convex

Question 8

Give the appearance of a plano-convex lens

Answer 8

It has one surface convex while the other is plane

Question 9

Give the appearance of a concavo-convex lens

Answer 9

It has one surface concave while the other is convex - it is thicker in the middle

Question 10

Give the appearance of a concave lens

Answer 10

It is thin in the middle and thick at its periphery - it is bent inward

Question 11

Name the three kinds of concave lens

Answer 11

1. Bi-concave
2. Plano-concave
3. Convexo-concave

Question 12

Give the difference between concavo-convex lens and convexo-concave lens in terms of appearance

Answer 12

A concavo-convex lens is thicker in the middle and has a converging action on an incident light beam, while a convexo-concave lens is thinner in the middle and has a diverging action on an incident light beam

Question 13

How do we consider a convex lens as a set of prisms?

Answer 13

A convex lens in its upper part has a prism with its base downwards, a rectangular slab, and in its lower part, a prism with its base upwards

Question 14

How do we consider a concave lens as a set of prisms?

Answer 14

A concave lens, in its upper part, has a prism with its base upwards, a rectangular slab in the middle, and a prism with its base downwards in the lower part

Question 15

How do we consider a concave lens as a set of prisms?

Answer 15

A concave lens, in its upper part, has a prism with its base upwards, a rectangular slab in the middle, and a prism with its base downwards in the lower part

Question 16

How does a convex lens have a converging action on an incident light beam?

Answer 16

The prism in the upper part of the convex lens bends the ray downwards towards the base, a second rays incident normally on the rectangular slab passes through undeviated, and the prism in the lower part of the prism bends the third ray upwards towards the base of the prism. Thus, the set of prisms converges the parallel rays to a point F

Question 17

How does a concave lens have a diverging action on an incident light beam?

Answer 17

The prism in the upper part of the concave lens bends the ray upwards towards the base, a second rays incident normally on the rectangular slab passes through undeviated, and the prism in the lower part of the prism bends the third ray downwards towards the base of the prism. Thus, the set of prisms diverges the parallel rays as if they are coming from a point F sitauted on the side of rays incident on the lens