NCERT Solutions for Class 10 Science Unit 11

Human Eye and Colourful World Class 10

Unit 11 Human Eye and Colourful World Exercise Solutions

The human eye is an organ that reacts to light and has several purposes. As a sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors.

Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.
<< Previous Chapter 10 : Light - Reflection and Refraction Next Chapter 12 : Electricity >>

Question : Solutions of Questions on Page Number : 190

Q1 :  

What is meant by power of accommodation of the eye?


Answer :

When the ciliary muscles are relaxed, the eye lens becomes thin, the focal length increases, and the distant objects are clearly visible to the eyes. To see the nearby objects clearly, the ciliary muscles contract making the eye lens thicker. Thus, the focal length of the eye lens decreases and the nearby objects become visible to the eyes. Hence, the human eye lens is able to adjust its focal length to view both distant and nearby objects on the retina. This ability is called the power of accommodation of the eyes.

Answer needs Correction? Click Here

Q2 :  

A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?


Answer :

The person is able to see nearby objects clearly, but he is unable to see objects beyond 1.2 m. This happens because the image of an object beyond 1.2 m is formed in front of the retina and not at the retina, as shown in the given figure.

To correct this defect of vision, he must use a concave lens. The concave lens will bring the image back to the retina as shown in the given figure.

Answer needs Correction? Click Here

Q3 :  

What is the far point and near point of the human eye with normal vision?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q4 :  

A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?


Answer :

Please Register/Login to get access to all solutions Facebook Login
<< Previous Chapter 10 : Light - Reflection and Refraction Next Chapter 12 : Electricity >>

Exercise : Solutions of Questions on Page Number : 197

Q1 :  

The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

(a) presbyopia

(b) accommodation

(c) near-sightedness

(d) far-sightedness


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q2 :  

The human eye forms the image of an object at its

(a) cornea (b) iris (c) pupil (d) retina


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q3 :  

The least distance of distinct vision for a young adult with normal vision is about

(a) 25 m

(b) 2.5 cm

(c) 25 cm

(d) 2.5 m


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q4 :  

The change in focal length of an eye lens is caused by the action of the

(a) pupil

(b) retina

(c) ciliary muscles

(d) iris


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q5 :  

A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q6 :  

The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q7 :  

Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q8 :  

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q9 :  

What happens to the image distance in the eye when we increase the distance of an object from the eye?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q10 :  

Why do stars twinkle?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q11 :  

Explain why the planets do not twinkle?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q12 :  

Why does the Sun appear reddish early in the morning?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q13 :  

Why does the sky appear dark instead of blue to an astronaut?


Answer :

Please Register/Login to get access to all solutions Facebook Login
<< Previous Chapter 10 : Light - Reflection and Refraction Next Chapter 12 : Electricity >>

Science : CBSE NCERT Exercise Solutions for Class 10th for Human Eye and Colourful World will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

Popular Articles