Ncert Science Class 10 Solutions Chapter 10 The Human Eye and the Colourful World
Welcome to NCTB Solutions. Here with this post we are going to help 10th class students for the Solutions of NCERT Class 10 Science Book Chapter 10, The Human Eye and the Colourful World. Here students can easily find step by step solutions of all the questions in The Human Eye and the Colourful World. Also our Expert Science Teacher’s solved all the problems with easily understandable language with proper guidance so that all the students can understand easily. Here in this post students will get chapter 10 solutions. Here all Question Answer are based on NCERT latest syllabus.
The Human Eye and the Colourful World Exercise question Solutions :
(1) The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to
Answer :
Correct option – (b) Accommodation
The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to Accommodation.
(2) The human eye forms the image of an object at its
Answer :
Correct option – (d) Retina
It is light sensitive screen on which image is formed. The human eye forms the image of an object at its Retina.
(3) The least distance of distinct vision for a young adult with normal vision is about.
Answer :
Correct option – (c) 25 cm
The least distance of distinct vision for a young adult with normal vision is about 25 cm.
(4) The change in focal length of an eye lens is caused by the action of the
Answer :
Correct option – (c) Ciliary muscles
The change in focal length of an eye lens is caused by the action of the Ciliary muscles.
(5) 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 :
F is focal length and p is lens power,
P = 1/f
For (i) distant vision We have f = -5.5 m
P = 1/-5.5
P = -0.1818 m
For (ii) near vision we have f = 1.5
P = 1/1.5
P = 0.66 m
(6) 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 :
As the person is myopic the vision can be corrected by concave lens.
Distance(v) = -80
Object distance(u) = ∞
Formulae of lens
1/v – 1/u = 1/f
1/-80 -1/∞ = 1/f
1/-80 = 1/f
f = -80 cm
f = -0.8 m
as P = 1/f
power(P) = 1/-0.8
P = -1.25 D
-1.25D powered concave lens is required.
(8) Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Answer :
The eye has ability to adjust its focal length but this ability have certain minimum limits, so in adult we can not see closer than 25 cm.
(9) What happens to the image distance in the eye when we increase the distance of an object from the eye?
Answer :
When we increase the distance of object from the eye, we eye adjust the image distance and the eye muscles relaxes which makes eye lens becomes thin. The focal length of eye is increases.
(10) Why do stars twinkle?
Answer :
The twinkling of stars is due to refraction of starlight, the starlight when enters earth surface the refraction of starlight continuously happens. As the stars are far away from earth they appears point sources of light. physical condition of atmosphere changes continuously. The path of rays may looks slightly different and changes continuously. The starlight may see flickering. Because of this the stars twinkles.
(11) Explain why the planets do not twinkle.
Answer :
Because, as compare to stars the planets are far near to the earth so atmospheric condition does not affect to planets, the planets looks expanded source of light. From all of the information the planets does not looks slightly different and does not changes continuously. That’s why planets doesn’t twinkle.
(12) Why does the sky appear dark instead of blue to an astronaut?
Answer :
The sky appear dark instead of blue to an Astronaut because,
In the earth atmosphere there is small tiny particles of dust and vapor which are smaller than the sunlight. When sunlight enters in the atmosphere the shorter wavelength which is off blue color gets scattered. That’s why the sky appears blue to us. But in the space where astronaut travel atmosphere is not present.so the sky appears dark because no scattering happens.
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