Class 10 Science · Chapter 10

The Human Eye and the Colourful World

163 Class 10 Science questions on The Human Eye and the Colourful World from the NCERT textbook, NCERT Exemplar and CBSE board papers 2023–2026, each with its answer and a step-by-step solution.

NCERT exercises

Exercises (12) Intext Questions (Page 164) (4)

NCERT Exemplar exercises

Multiple Choice Questions (14) Short Answer Questions (10) Long Answer Questions (6)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 5 of 9

Q81 CBSE 2026
1. (a)What is Tyndall effect ?
2. (b)What happens when sunlight is scattered from the particles of very large size ?
3. (c)‘Danger’ signals are always red in colour. Why ?
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Tyndall effect is scattering by colloidal particles; very large particles give white light; red is scattered least, so it is seen from far.
(a) The Tyndall effect is the scattering of a beam of light by the colloidal particles in its path (such as smoke or dust in air), which makes the path of the beam visible - for example, a sunbeam entering a smoky room through a small hole. (b) Particles of very large size scatter all the colours of sunlight almost equally, so the scattered light appears white; this is why clouds look white. (c) Red light has the longest wavelength in the visible spectrum, so it is scattered the least by air and by the fine particles of smoke, dust and mist; it therefore travels farthest and can be seen, in the same colour, from a large distance.

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Q82 CBSE 2026
1. (a)What is hypermetropia ?
2. (b)Write any one cause of hypermetropia.
3. (c)With the help of a suitable ray diagram, explain how hypermetropia is corrected ?
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Hypermetropia: nearby objects look blurred (near point beyond 25 cm); eye-lens focal length too long is one cause; a convex lens corrects it.
(a) Hypermetropia (far-sightedness) is the defect of vision in which a person can see distant objects clearly but cannot see nearby objects distinctly: the near point of the eye lies farther than the normal $25$ cm, because light from a nearby object is focused behind the retina. (b) Cause (any one): the focal length of the eye lens becomes too long (the eye lens is not converging enough), or the eyeball becomes too small. (c) It is corrected with spectacles having a convex (converging) lens of suitable power. The convex lens bends the rays from an object at N, $25$ cm away, so that they appear to come from the near point N′ of the defective eye; the eye can focus light from N′, so the image is formed on the retina. In the ray diagram, rays from N pass through the convex lens, their backward extensions meet at N′, and the eye lens brings them to a focus on the retina.

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Q83 CBSE 2026

A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate the defect. List two possible causes of this defect also.

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Hypermetropia: the near point is 50 cm, so closer objects focus behind the retina; a long focal length or short eyeball causes it.
The defect is hypermetropia, also called far-sightedness or long-sightedness. The nearest point this eye can focus on has moved out from the normal $25$ cm to $50$ cm, so light coming from anything closer than $50$ cm is brought to a focus behind the retina and the image on the retina is blurred; distant objects are still seen clearly. The ray diagram shows light from an object at the normal near point of $25$ cm meeting behind the retina, and light from an object at $50$ cm meeting exactly on it. Two possible causes: (i) The focal length of the eye lens is too long, so its converging power is too low; (ii) The eyeball is too short, so the retina lies in front of the point where the refracted rays meet.

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Q84 CBSE 2026
Read the following passage and answer the questions that follow : Two students, A and B were performing an activity on refraction through glass slab and refraction through prism respectively. Student ‘A’ observed that the emergent light ray is parallel to the direction of incident ray, while student ‘B’ observed that the emergent ray is making a certain angle with respect to the direction of the incident ray in the prism, called angle of deviation. He also noted that the angle of deviation is different for different colours of light.
1. (a)When white light passes through a glass slab, it does not show dispersion, while it shows dispersion when it passes through a glass prism. Why ?[1]
2. (b)Why do we get spectrum when white light passes through tiny water droplets present in air ?[1]
3. (c)(i)For a given pair of mediums, if we change the angle of incidence gradually, will it change the speed of light in that medium ? Explain.[2]
4. (c)(ii)OR : Calculate the speed of light in a given medium if angle of incidence in air is $6 0^{\circ}$ and angle of refraction in the medium is $3 0^{\circ}$ . Given that speed of light in air is $3 \times 1 0^{8}$ m/s.[2]
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Parallel slab faces cancel dispersion, inclined prism faces add it; droplets act as prisms; speed does not depend on $i$ ; OR $v = 1.73 \times 1 0^{8}$ m/s.
(a) White light is dispersed at the first refracting surface in both cases, because glass has a slightly different refractive index for each colour. The two faces of a glass **slab** are parallel, so the refraction at the second face is equal and opposite to that at the first; the colours recombine and the emergent beam is white, parallel to the incident beam and only shifted sideways. The two faces of a **prism** are inclined to each other, so the deviations at the two faces add instead of cancelling, each colour leaves in a different direction, and a spectrum is seen. (b) The tiny water droplets act as tiny prisms. Sunlight entering a droplet is refracted and dispersed at its surface, the separated colours are reflected internally at the back surface of the drop, and they are refracted and dispersed again as they leave the drop. Each colour is deviated by a different total amount, so the light emerging is spread into a band of colours — the spectrum we see as a rainbow. (c)(i) No. The speed of light in a medium is $v = c / n$ , and the refractive index $n$ is a property of the medium and of the colour of the light, not of the angle of incidence. Changing the angle of incidence changes the angle of refraction in just the way that keeps $sin i / sin r$ equal to the same $n$ , so the light travels in a different direction inside the medium but at the same speed. (c)(ii) $n = \frac{sin 6 0 ^{\circ}}{sin 3 0 ^{\circ}} = \frac{3 /2}{1/2} = 3$ , so $v = \frac{c}{n} = \frac{3 \times 1 0 ^{8}}{3} = 3 \times 1 0^{8} = 1.73 \times 1 0^{8}$ m/s.

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Q85 CBSE 2025
When a beam of white light passes through a region of very fine dust particles, the colour of light that scatters the most in that region is :
1. (a)red
2. (b)orange
3. (c)blue
4. (d)yellow
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(c) blue

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Q86 CBSE 2025
Select the correct statement from the following :
1. (a)The size of the molecules of air is larger than the wavelength of visible light.
2. (b)The blue light has a wavelength about 1.8 times greater than that of red light.
3. (c)When sunlight passes through the fine particles in air, they scatter the blue colour of visible light more strongly than red.
4. (d)The light of red colour is scattered the most by fog or smoke.
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(c) When sunlight passes through the fine particles in air, they scatter the blue colour of visible light more strongly than red.

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Q87 CBSE 2025
In the given figure the angle of incidence and the angle of deviation respectively are :
1. (a) $1$ and $5$
2. (b) $7$ and $6$
3. (c) $7$ and $4$
4. (d) $1$ and $6$
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(d) $1$ and $6$

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Q88 CBSE 2025
The white light entering a glass prism, gets split into its constituent colours. It is observed that :
1. (a)Red light deviates the most.
2. (b)Violet light deviates the least.
3. (c)Yellow light deviates more than the blue light.
4. (d)Green light deviates more than the orange light.
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(d) Green light deviates more than the orange light.

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Q89 CBSE 2025
In the human eye, most of the refraction for the light rays entering the eye occurs at the surface of :
1. (a)Cornea
2. (b)Crystalline lens
3. (c)Pupil
4. (d)Aqueous humor
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(a) Cornea

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Q90 CBSE 2025
The part of the human eye which can modify the curvature of the eye lens to some extent is :
1. (a)Pupil
2. (b)Cornea
3. (c)Ciliary muscles
4. (d)Aqueous humour
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(c) Ciliary muscles

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Q91 CBSE 2025
The curvature of eye lens of human eye
1. (a)is fixed.
2. (b)can be increased.
3. (c)can be decreased.
4. (d)increases or decreases as the case may be.
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(d) increases or decreases as the case may be.

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Q92 CBSE 2025
An old person is suffering from an eye defect caused by weakening of ciliary muscles and diminishing flexibility of the eye lens. If the defect of vision is ‘a’ which can be corrected by lens ‘b’, then ‘a’ and ‘b’ respectively are :
1. (a)hypermetropia and convex lens
2. (b)presbyopia and bifocal lens
3. (c)myopia and concave lens
4. (d)myopia and bifocal lens
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(b) presbyopia and bifocal lens

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Q93 CBSE 2025
Select the correct statements from the following in the context of the human eye :
1. (i)Most of the refraction of light rays entering the eye occurs at the crystalline lens.
2. (ii)The diameter of the eye ball is about $2.3$ cm.
3. (iii)Iris is a dark muscular diaphragm which controls the size of the pupil.
4. (iv)While focusing on the objects at different distances, the distance between the lens and the retina is adjusted by the ciliary muscles.
1. (a)(i) and (iv)
2. (b)(ii) and (iii)
3. (c)(i), (ii) and (iv)
4. (d)(ii), (iii) and (iv)
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(b) (ii) and (iii)

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Q94 CBSE 2025
The possible way to restore clear vision of those people whose eyeball has elongated is the use of suitable
1. (a)bifocal lens
2. (b)concave lens
3. (c)converging lens
4. (d)convex lens
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(b) concave lens

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Q95 CBSE 2025
The part of human eye which controls the amount of light entering into it.
1. (a)Iris
2. (b)Cornea
3. (c)Ciliary muscles
4. (d)Pupil
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(a) Iris

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Q96 CBSE 2025
When we focus our eyes on a distance object, the ciliary muscles of our eyes are relaxed. In this case the eye lens becomes
1. (a)thin and its curvature is maximum.
2. (b)thin and its curvature is minimum.
3. (c)thick and its curvature is minimum.
4. (d)thick and its curvature is maximum.
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(b) thin and its curvature is minimum.

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Q97 CBSE 2025
A boy while reading a book, keeps it much beyond $25$ cm from his eyes. This defect of vision has arised because of
1. (a)excessive curvature of the eye lens
2. (b)the focal length of the eye lens has increased
3. (c)the eye ball has elongated
4. (d)the focal length of the eye lens has become too small
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(b) the focal length of the eye lens has increased

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Q98 CBSE 2025
Most of the refraction for the light rays entering the eye occurs at
1. (a)Iris
2. (b)Pupil
3. (c)Crystalline lens
4. (d)Outer surface of Cornea
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(d) Outer surface of Cornea

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Q99 CBSE 2025
The phenomenon responsible for making the smoke particles visible when a beam of sunlight enters a smoke filled room through a narrow hole is :
1. (a)scattering of light
2. (b)dispersion of light
3. (c)reflection of light
4. (d)internal reflection of light
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(a) scattering of light

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Q100 CBSE 2025
Consider the following ray diagram : Here, the angle of incidence and angle of deviation respectively are
1. (a)a and e
2. (b)b and d
3. (c)b and e
4. (d)a and f
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(c) b and e

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