Solutions of The Human Eyes And The Colorful Wor (Page No- 272) - Physics By Lakhmir Singh, Class 10 | Extra Documents, Videos & Tests for Class 10 PDF Download

Lakhmir Singh Physics Class 10 Solutions Page No:272

Question 53: he descriptions of five kinds of images are given below :
 (a) diminished and virtual
 (b) enlarged and real
 (c) enlarged and erect
 (d) real and inverted
 (e) virtual and the same size
 Which one of these describes the image formed :

1. on the retina of the eye ?
2. by a magnifying glass ?
3. by a convex driving mirror on a car ?
4.  by a plane mirror ?
5. on the screen of a slide projector ?

Solution :

1. d
2. c
3. a
4. e
5. b

Question 54: What shape are your eye-lenses :
 (a) when you look at your hand ?
 (b) when you look at a distant tree ?

Solution : (a) Thick
(b) Thin

Question 55: Suggest how your irises help to protect the retinas of your eyes from damage by bright light.

Solution : Irises help to protect the retinas of our eyes from damage by bright light by adjusting the size of the pupil according to the intensity of light received by the eye.

Question 56: (a) Which parts of the eye cause rays of light to converge on the retina ?
 (b) Which part causes the greatest convergence ?
 (c) Which part brings the image into sharp focus on the retina ? How does it do this ?

Solution : (a) Cornea and eye-lens
(b) Cornea
(c) Eye lens
By changing its thickness and hence conversing power.

Question 57: An object is moved closer to an eye. What changes must take place in the eye in order to keep the image in sharp focus ?

Solution : Ciliary muscles should change the shape of eyes-lens to make it thicker and increase its converging power.

Question 58: Why does the eye-lens not have to do all the work of converging incoming light rays ?

Solution : The eye-lens does not have to do all the work of converging incoming light rays because cornea of the eye also converges light rays entering the eye.

Question 59: Explain why, when it is getting dark at night, it is impossible to make out the colour of cars on the road.

Solution : The color detecting cells of the retina of the eye called ‘cones’ do not work well in dim light.

Question 60: Nocturnal animals (animals which sleep during the day and come out at night) tend to have wide pupils and lot of rods in their retinas. Suggest reasons for this.

Solution : Wide pupils allow more light to enter the eye during night.

Rod cells in the retina are sensitive to dim light and hence help in seeing properly at night.