Class 10 Science · Chapter 10

The Human Eye and the Colourful World

281 Class 10 Science questions on The Human Eye and the Colourful World from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 7 of 15

1. Q121 CBSE 2025
   1. (i)Name and explain the phenomenon of light responsible ​to make the path of a beam of light visible when it enters a ​smoke/dust-filled room through a small hole. Also state the dependence of ​the colour of the light we receive on the size of the particles of the medium through which the light ​passes.
   2. (ii)A person suffering from presbyopia needs spectacles having bifocal lenses. If the power of two lenses used in his spectacles is $+2.0$ D ​and $-0.5$ D, which one of ​the two lenses is ​for the correction of his distant vision and what is its focal length ?
   Show answer

   Tyndall effect makes the beam visible, with fine particles scattering blue; the concave $-0.5$ D lens is for distant vision, with $f=-2$ m.

   (i) The phenomenon is the Tyndall effect, the scattering of light by the tiny particles of smoke and dust suspended in the air. As the beam passes through the room these particles scatter the light in all directions, and some of the scattered light reaches our eyes from the side, so the whole path of the beam becomes visible. The colour of the light we receive depends on the size of the scattering particles: very fine particles scatter mainly blue light, that is light of shorter wavelengths, while particles of larger size scatter light of longer wavelengths, and if the particles are large enough the scattered light may even appear white. (ii) In a bifocal lens the upper concave portion corrects distant vision and the lower convex portion is used for reading. Since $P=1/f$, a negative power means a concave, diverging lens, so the lens for the correction of distant vision is the one of power $-0.5$ D. Its focal length is $f=1/P=1/(-0.5)=-2$ m, that is $-200$ cm.

   Step-by-step solution →
2. Q122 CBSE 2025
   1. (i)What is ​hypermetropia ? List its ​two possible causes. Name the type of lens ​used to correct this defect ​and state its role in this case.
   2. (ii)A person suffering from presbyopia needs bifocal lens. If he needs two lenses of power $+2.5$ D and $-0.25$ D, which one ​of ​these two lenses is for the correction of distant vision and what is its focal ​length ?
   Show answer

   Hypermetropia is corrected by a convex lens; the concave $-0.25$ D lens is for distant vision, with $f=-4$ m.

   (i) Hypermetropia, or 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 at a point behind the retina. Two possible causes: (1) the focal length of the eye lens is too long; (2) the eyeball has become too small. It is corrected with a convex (converging) lens of suitable power. Its role: it supplies the extra converging power the eye lacks, making light from an object at $25$ cm seem to come from the person's own near point, so that the eye lens can form the image on the retina. (ii) Since $P=1/f$, the $-0.25$ D lens is diverging (concave) and the $+2.5$ D lens converging (convex). In a common bifocal lens the upper concave portion serves distant vision and the lower convex portion near vision, so the lens for the correction of distant vision is the one of power $-0.25$ D. Its focal length is $f=1/P=1/(-0.25)=-4$ m, that is $-400$ cm.

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3. Q123 CBSE 2025
   A person allowed ​a narrow beam of ​white light from the sun to enter a dark room through a small aperture and placed a ​glass prism in its path in such ​a manner that the ​beam falls on the face AB of the prism as shown in the figure. A screen ​S is placed ​on the other side of the prism, facing AC. On turning the prism slowly, ​a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.

   1. (a)Name the phenomenon due to which a prism splits the incident white light into a band of colours.[1]
   2. (b)State the reason of getting a band of seven colours in the above case.[1]
   3. (c)(i)Explain with the help of a labelled ray diagram, an experimental arrangement to show the recombination of the spectrum of white light.[2]
   4. (c)(ii)OR : Draw a labelled ray diagram to show the formation of a rainbow.[2]
   Show answer

   Dispersion; each colour has a different refractive index and bends differently; an inverted second prism recombines the colours; raindrops disperse sunlight into a rainbow.

   (a) Dispersion, that is, the dispersion of white light. (b) Sunlight is a mixture of seven colours, and the glass of the prism has a different refractive index for each of them, so each colour is deviated through a different angle - violet the most and red the least. The colours therefore emerge along different paths, become distinct and are seen as a band of seven colours (VIBGYOR). (c)(i) Newton's two-prism arrangement: a narrow beam of white light is dispersed by a first prism P1 held apex upwards, and a second identical prism P2 is placed close behind it in an inverted position so that all the colours of the spectrum pass through it. P2 deviates every colour by an equal angle in the opposite sense, so the deviations cancel colour by colour, the colours merge and a beam of white light emerges from P2 and is caught on the screen (see the labelled ray diagram). (c)(ii) A rainbow forms in tiny water droplets left hanging after a rain shower, with the Sun behind the observer. Sunlight entering a droplet is refracted and dispersed at the first surface, is reflected at the inside of the far surface, and is refracted again as it leaves the droplet. The colours emerge at slightly different angles - about $42^{\circ }$ for red and about $40^{\circ }$ for violet - so different droplets send different colours to the eye and the bow appears with red on the outside and violet on the inside (see the labelled ray diagram).

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4. Q124 CBSE 2025
   The students in a class took a thick sheet of ​cardboard ​and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a ​narrow beam of white light. A glass prism was taken and this white light ​was allowed to fall on one of its faces. The prism ​was turned slowly until ​the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band ​of light and concluded that it is a ​spectrum of white light.

   1. (i)Give any one more instance in which this type of spectrum is observed.[1]
   2. (ii)What happens to white light in the above case?[1]
   3. (iii)(A)List two conditions necessary to observe a rainbow.[2]
   4. (iii)(B)OR : Draw a ray diagram to show the formation of a rainbow. Mark on it, points (a), (b) and (c) as given below : (a) Where dispersion of light occurs. (b) Where light gets reflected internally. (c) Where final refraction occurs.[2]
   Show answer

   A rainbow is another spectrum; white light disperses into VIBGYOR in a prism; a rainbow needs water droplets and the Sun behind the observer.

   (i) A rainbow in the sky after a rain shower is the same kind of spectrum; so is the band of colours seen on looking at the sky through the spray of a waterfall or a fountain with the Sun behind you. (ii) The white light is dispersed - it splits into its seven component colours, violet, indigo, blue, green, yellow, orange and red (VIBGYOR), forming a band called the spectrum, because the glass has a different refractive index for each colour and so deviates violet the most and red the least ($n_{\text{violet}}>n_{\text{red}}$). (iii)(A) Two conditions: (1) there must be water droplets suspended in the air in front of the observer, as during or just after a rain shower; and (2) the Sun must be shining behind the observer, so that the observer faces the droplets with the Sun at their back - a rainbow is always formed in the direction opposite to the Sun. (iii)(B) In the ray diagram of a raindrop: (a) is on the surface where the sunlight enters, where it is refracted and dispersed; (b) is on the far inside surface, where the dispersed light is reflected internally; and (c) is on the lower surface, where the light is refracted again as it leaves the drop and the separated colours travel on to the observer.

   Step-by-step solution →
5. Q125 CBSE 2025
   The human eye is ​one of the most valuable and sensitive sense organs. Eyes enable us ​to see the wonderful world around us. We observe that some persons cannot ​see ​the objects distinctly and comfortably. The vision ​becomes blurred ​due to the refractive ​defects of the ​eye.

   1. (a)When do we say that a person is suffering from myopia ?
   2. (b)List two main causes of myopia.
   3. (c)(i)When do we say that a person is suffering from presbyopia. Write the structure of common type of bifocal lenses used by the persons suffering from presbyopia.
   4. (c)(ii)OR : A person is using corrective lenses of power $+0.25$ D in his spectacles for seeing the objects clearly. Name the defect of vision he is suffering from. Also calculate the focal length of the lenses used in his spectacles.
   Show answer

   Myopia: nearby objects clear, distant ones not; causes are a too curved lens or a long eyeball; presbyopia needs bifocals; OR hypermetropia, $f=+4$ m.

   (a) A person is suffering from myopia when he can see nearby objects clearly but cannot see distant objects distinctly and comfortably: his far point has come in from infinity to a finite distance and the image of a distant object is formed in front of the retina. (b) The two main causes are excessive curvature of the eye lens, which gives the eye too much converging power, and elongation of the eyeball, which puts the retina too far behind the lens. (c)(i) A person is suffering from presbyopia when his power of accommodation has decreased with age, so that the near point recedes and he cannot see nearby objects clearly; it is due to the weakening of the ciliary muscles and the loss of flexibility of the eye lens. The common bifocal lens consists of both a concave and a convex lens: the upper portion is a concave lens for distant vision and the lower portion is a convex lens for near vision. (c)(ii) The power is positive, so the lens is convex and the defect is hypermetropia (far-sightedness). Its focal length is $f=\frac{1}{P}=\frac{1}{0.25}=+4$ m $=+400$ cm.

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6. Q126 CBSE 2024
   Consider the following statements : i. Ciliary muscles ​adjust for changing the intensity of light entering the eye. ii. Myopic eye can ​be corrected ​by converging lenses of suitable power. iii. The function of the ​pupil is to regulate ​the quantity of light entering the eye. iv. When ciliary muscles are completely relaxed, the focal length of the eye lens is maximum. The correct ​statements are ​:

   1. (a)i, ii and iv
   2. (b)i, ii and iii
   3. (c)iii and iv
   4. (d)ii and iv
   Show answer

   (c) iii and iv

   Step-by-step solution →
7. Q127 CBSE 2024
   When ​a beam of ​white light passes through a region having very fine dust particles, ​the colour ​of ​light mainly scattered ​in that region ​is :

   1. (a)Red
   2. (b)Orange
   3. (c)Blue
   4. (d)Yellow
   Show answer

   (c) Blue

   Step-by-step solution →
8. Q128 CBSE 2024
   The ​phenomena ​of light involved ​in ​the formation ​of rainbow ​are ​:

   1. (a)Refraction, reflection and dispersion
   2. (b)Refraction, dispersion and internal reflection
   3. (c)Reflection, dispersion and internal reflection
   4. (d)Refraction, dispersion, scattering and total internal reflection
   Show answer

   (b) Refraction, dispersion and internal reflection

   Step-by-step solution →
9. Q129 CBSE 2024
   The ​lens system of ​human eye forms an ​image ​on a ​light sensitive screen, which is called as :

   1. (a)Cornea
   2. (b)Ciliary muscles
   3. (c)Optic nerves
   4. (d)Retina
   Show answer

   (d) Retina

   Step-by-step solution →
10. Q130 CBSE 2024
    Consider the following statements in the context ​of human eye :

    1. (a)The diameter of the ​eye ball ​is about 2.3 cm.
    2. (b)​Iris is ​a dark muscular diaphragm that controls the size of the pupil.
    3. (c)Most of the ​refraction for the light rays entering the ​eye occurs at the crystalline lens.
    4. (d)While focusing on the objects at different ​distances the distance between the crystalline lens and the retina is adjusted by ciliary muscles. The correct statements are –

    1. (a)(a) and (b)
    2. (b)(a), (b) and (c)
    3. (c)(b), (c) and (d)
    4. (d)(a), (c) and (d)
    Show answer

    (a) (a) and (b)

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11. Q131 CBSE 2024
    The Phenomena of light involved ​in the ​formation of ​a ​rainbow in ​the ​sky ​are

    1. (a)Refraction, dispersion and reflection
    2. (b)Refraction, dispersion and total internal reflection
    3. (c)Dispersion, scattering and reflection
    4. (d)Dispersion, refraction and internal reflection
    Show answer

    (d) Dispersion, refraction and internal reflection

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12. Q132 CBSE 2024
    The ​colour of ​light for which ​the refractive ​index ​of glass ​is ​minimum, is :

    1. (a)Red
    2. (b)Yellow
    3. (c)Green
    4. (d)Violet
    Show answer

    (a) Red

    Step-by-step solution →
13. Q133 CBSE 2024
    In ​bifocal lenses ​used ​for ​the correction ​of presbyopia ​:

    1. (a)the upper portion is of convex lens for the near vision and lower part is of concave lens for the distant vision.
    2. (b)the upper portion is of convex lens for the distant vision and lower part is of concave lens for the near vision.
    3. (c)the upper portion is of concave lens is for the near vision and lower part is of convex lens for the distant vision.
    4. (d)the upper portion is of concave lens for the distant vision and lower part is of convex lens for the near vision.
    Show answer

    (d) the upper portion is of concave lens for the distant vision and lower part is of convex lens for the near vision.

    Step-by-step solution →
14. Q134 CBSE 2024
    A person is advised to use ​lenses ​of ​power $-0.25$ D for the ​correction of ​his defect of ​vision. It ​implies that the person is suffering from :

    1. (a)hypermetropia and he has to use converging lens of focal length $25$ cm in his spectacles.
    2. (b)hypermetropia and he has to use diverging lens of focal length $4$ m in his spectacles.
    3. (c)myopia and he has to use diverging lens of focal length $4$ m in his spectacles.
    4. (d)myopia and he has to use diverging lens of focal length $25$ cm in his spectacles.
    Show answer

    (c) myopia and he has to use diverging lens of focal length $4$ m in his spectacles.

    Step-by-step solution →
15. Q135 CBSE 2024
    These questions consist of two statements – ​Assertion (A) ​and Reason ​(R). ​Answer these ​questions ​selecting ​the appropriate option given below :

    Assertion (A): Myopic eye cannot see distant objects distinctly.

    Reason (R): For the correction of myopia converging lenses of appropriate power are prescribed by eye-surgeons.

    1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
    2. (b)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
    3. (c)(A) is true, but (R) is false.
    4. (d)(A) is false, but (R) is true.
    Show answer

    (c) (A) is true, but (R) is false.

    Step-by-step solution →
16. Q136 CBSE 2024
    These questions consist of ​two ​statements – ​Assertion (A) ​and Reason (R). Answer ​these ​questions selecting the appropriate option given ​below :

    Assertion (A): The colour of clear sky appears blue.

    Reason (R): Light of blue colour has longer wavelength as compared to the light of red colour so it is scattered more in the upper atmosphere.

    1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
    2. (b)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
    3. (c)(A) is true, but (R) is false.
    4. (d)(A) is false, but (R) is true.
    Show answer

    (c) (A) is true, but (R) is false.

    Step-by-step solution →
17. Q137 CBSE 2024
    Q. Nos. ​17 to ​20 consists ​of two statements ​– Assertion (A) ​and Reason (R), answer ​these questions selecting the appropriate ​option given ​below :

    Assertion (A): Red light signals are used to stop the vehicles on the road.

    Reason (R): Red coloured light is scattered the most so as to be visible from a large distance.

    1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
    2. (b)Both (A) and (R) are true and (R) is not correct explanation of (A).
    3. (c)(A) is true, but (R) is false.
    4. (d)(A) is false, but (R) is true.
    Show answer

    (c) (A) is true, but (R) is false.

    Step-by-step solution →
18. Q138 CBSE 2024
    Two statements ​are given – ​one labelled ​as Assertion (A) and the other labelled as Reason (R). Select ​the correct answer ​to these questions from the codes (a), (b), ​(c) and (d) as ​given below :

    Assertion (A): The rainbow is a natural spectrum of sunlight in the sky.

    Reason (R): Rainbow is formed in the sky when the sun is overhead and water droplets are also present in air.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (c) Assertion (A) is true, but Reason (R) is false.

    Step-by-step solution →
19. Q139 CBSE 2024
    When ​do ​we say that ​a particular person is suffering ​from ​hypermetropia ? List two causes of this defect. Name the type of lens used to correct this ​defect.
    Show answer

    In hypermetropia nearby objects are not seen clearly because the near point is beyond 25 cm; a convex lens corrects it.

    A person is said to suffer from hypermetropia (far-sightedness) when distant objects are seen clearly but nearby objects cannot be seen distinctly: the near point of the eye is farther away than the normal near point of 25 cm, because light from a nearby object is focused behind the retina. Two causes: (i) the focal length of the eye lens is too long; (ii) the eyeball has become too small. The defect is corrected with a convex (converging) lens of suitable power.

    Step-by-step solution →
20. Q140 CBSE 2024
    A person suffering from presbyopia needs bifocal lens. If ​he needs two lens ​of ​power $-4.0$ ​dioptre and $+2.0$ dioptre, ​which one of these two ​lenses is for the correction ​of distant vision and what is its ​focal length ?
    Show answer

    The concave lens of power $-4.0$ D corrects distant vision; its focal length is $-25$ cm.

    The concave lens of power $-4.0$ D (the upper part of the bifocal lens) is for the correction of distant vision. Its focal length is $f=\frac{1}{P}=\frac{1}{-4.0\text{D}}=-0.25$ m $=-25$ cm; the minus sign shows that it is a diverging (concave) lens.

    Step-by-step solution →