Question

44. Answer the following questions as directed :

(1) Give scientific reason: It is difficult to pierce a fish swimming in a river.
(2) Give two points of differences : Convex lens and Concave lens
(3) Define the following with reference to convex lens:
(1) Centre of curvature ( 2 ) Focal length​

Answer 1

I hope it helps you! have a nice day

Answer 2

Answers are as follows-

1. It is difficult to pierce a fish swimming in water due to phenomenon of refraction. Light rays travel from fish in water to human eyes in air. This causes deviation of light rays away from the normal and hence human aims at apparent position of fish rather than real position.

2. Convex lens is thicker in middle while concave lens is thinner in middle. Moreover, at edges convex lens is thinner and concave lens is thicker.

Convex lens converges the incident light rays while concave lens diverges them.

3. 1. Centre of curvature of a lens is defined as the centre of sphere from which lens is made of.

2. Focal length of a lens is the distance between optical centre and focus of lens.