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 6 of 15

1. Q101 CBSE 2025
   Two statements are given below – one labelled as Assertion ​(A) and the other ​labelled as Reason ​(R). Select the ​correct answer ​to this question from ​the options (a), ​(b), (c) and (d) given below.

   Assertion (A): The colour of the scattered light depends on the size of the scattering particles.

   Reason (R): Very fine particles scatter mainly red light while particles of larger size scatter light of shorter wavelengths.

   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 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 →
2. Q102 CBSE 2025
   Two ​statements are given below ​— one labelled ​as Assertion (A) ​and the other labelled as Reason (R). Select the ​correct answer to ​this question ​from the codes (a), (b), (c) ​and (d) as given below.

   Assertion (A): Due to scattering of sunlight, the clear sky predominantly appears blue.

   Reason (R): The wavelength of blue light is nearly $1.8$ times the wavelength of red light.

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

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3. Q103 CBSE 2025
   Two statements ​are given — one labelled Assertion (A) and the other labelled Reason (R). ​Select ​the ​correct answer ​to this question from the codes (a), (b), (c) and (d) ​given ​below.

   Assertion (A): When ciliary muscles contract, eye lens becomes thin.

   Reason (R): Ciliary muscles control the power of the eye lens.

   1. (a)Both, Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both, Assertion (A) and Reason (R) are true, and Reason (R) is not the correct explanation of 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

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

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4. Q104 CBSE 2025
   This question consists of two statements – Assertion (A) and ​Reason ​(R). Answer ​this question ​selecting ​the ​appropriate ​option ​(a), (b), (c) and (d) as given below :

   Assertion (A): White light is dispersed by a glass prism into seven colours.

   Reason (R): The red light bends the least while the violet the most when a beam of white light passes through a glass prism.

   1. (a)Both, Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both, Assertion (A) and Reason (R) are true, and Reason (R) is not the correct explanation of 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

   (a) Both, Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).

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5. Q105 CBSE 2025
   A student has difficulty ​in reading his textbooks but can read the blackboard clearly while ​sitting in the last row. Name the defect of vision the student ​is suffering ​from. List two reasons ​due to which this defect arises. Write the ​nature ​of the lenses ​required to correct this defect.
   Show answer

   Hypermetropia, caused by a long eye-lens focal length or a short eyeball, corrected with a convex lens.

   The defect is hypermetropia (far-sightedness). It arises because (i) the focal length of the eye lens has become too long, so the lens converges the rays too little, or (ii) the eyeball has become too short from front to back, so the retina lies in front of the image. It is corrected with a convex (converging) lens of suitable power, which brings the rays from a near object to a focus on the retina.

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6. Q106 CBSE 2025
   Draw a ray ​diagram to show the refraction of a ray of light passing through an equilateral ​glass ​prism. ​Mark the angle through which ​the emergent ​ray bends from the ​direction of the ​incident ray and also name it.
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   The emergent ray turns towards the base; the angle between incident and emergent rays is the angle of deviation $\angle D$.

   The ray bends towards the normal on entering the glass at the first face and away from the normal on leaving at the second face, and it emerges turned towards the base of the prism. The angle between the direction of the incident ray produced and the emergent ray is the **angle of deviation**, $\angle D$. For the drawn construction, with $\angle A=60^{\circ }$, $n=1.5$ and $\angle i=45^{\circ }$, the angles are $\angle r_1=28.1^{\circ }$, $\angle r_2=31.9^{\circ }$, $\angle e=52.4^{\circ }$ and $\angle D=\angle i+\angle e-\angle A=37.4^{\circ }$.

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7. Q107 CBSE 2025
   Give ​reasons ​:

   1. (i)​The sky appears dark ​to passengers flying at very ​high ​altitude.
   2. (ii)‘Danger’ signal lights are ​red ​in colour.
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   (i) Thin air at high altitude scatters little light, so the sky looks dark; (ii) red is scattered the least, so it is seen farthest.

   (i) At a very high altitude the atmosphere is extremely thin, so there are very few air molecules and dust particles to scatter sunlight. Hardly any scattered light reaches the passengers' eyes, so the sky appears dark to them instead of blue. (ii) Red light has the longest wavelength of the visible colours, and scattering falls off steeply as the wavelength grows, so red is scattered the least by fog, smoke and dust. It therefore travels the farthest and is visible from the greatest distance, which is what a danger signal needs.

   Step-by-step solution →
8. Q108 CBSE 2025
   Draw ​a ray diagram to show the path ​of ​a ray of light falling obliquely ​on one of the refracting faces ​of a triangular glass ​prism and mark the angle of ​deviation on ​it.
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   The ray bends towards the normal at the first face and away at the second, turning towards the base; $\delta =i+e-A$.

   The ray bends towards the normal on entering the prism at $P$, travels straight to $Q$ on the second face, and bends away from the normal on emerging, so that it is turned towards the base of the prism. The angle of deviation $\delta$ is marked between the produced incident ray and the emergent ray, where $\delta =i+e-A$. For the diagram drawn ($A=60^{\circ }$, $n=1.5$, $i=45^{\circ }$): $r_1=28.1^{\circ }$, $r_2=31.9^{\circ }$, $e=52.4^{\circ }$ and $\delta =37.4^{\circ }$.

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9. Q109 CBSE 2025
   Name the ​type of ​lenses required by ​the ​persons for the correction of their defect ​of vision called presbyopia. Write the structure of the lenses commonly used for ​the correction of ​this ​defect giving reason for such designs.
   Show answer

   A convex lens corrects presbyopia; bi-focal lenses, with a concave upper and convex lower part, correct distant and near vision together.

   Presbyopia is corrected with a **convex** (converging) lens, because the defect is a loss of the power of accommodation and it is near vision that fails. Sometimes such a person also suffers from myopia and then needs correction for distant as well as near vision; for this the lenses commonly used are **bi-focal lenses**. Structure: the upper part of each lens is a concave lens and the lower part is a convex lens. Reason: distant objects are viewed by looking straight ahead, through the upper concave part which corrects distant vision, while reading is done by looking downwards, through the lower convex part which corrects near vision — so one pair of spectacles corrects both defects.

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10. Q110 CBSE 2025
    What ​is a ​rainbow ? “We ​see a ​rainbow ​in the sky ​only after the rainfall.” ​Why ?
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    A rainbow is a spectrum formed by dispersion of sunlight in water droplets, so it is seen only after rain.

    A rainbow is a natural spectrum, an arc of seven colours, that appears in the sky after a rain shower. It is caused by the dispersion of sunlight by the tiny water droplets suspended in the atmosphere: each droplet acts as a small prism, so sunlight entering it is refracted and dispersed, then reflected internally at the inner surface at the back of the drop, and refracted again as it leaves. The colours emerge separated, red at about $42^{\circ }$ and violet at about $41^{\circ }$ to the direction of the sunlight, and the rainbow is always seen opposite the Sun. We see it only after rainfall because only then are tiny water droplets suspended in the air to act as those prisms; without the droplets there is nothing to disperse the sunlight.

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11. Q111 CBSE 2025
    Draw a ray diagram ​to show ​the path of a ray ​of light which falls obliquely on one ​of the faces of an equilateral triangular prism ​made of glass and mark on it the ​angle of ​incidence ($\angle i$) and the angle of deviation ($\angle D$).
    Show answer

    The ray bends towards the normal at $AB$ and away at $AC$, giving angle of deviation $\angle D=37.4^{\circ }$ for $\angle i=45^{\circ }$.

    The ray diagram is shown in the figure. The ray strikes the face $AB$ obliquely, bends towards the normal on entering the glass, travels across the prism, and bends away from the normal as it emerges from the face $AC$, so it is deviated towards the base. The angle of incidence $\angle i$ is marked between the incident ray and the normal at the first face, and the angle of deviation $\angle D$ is marked between the incident ray produced forward and the emergent ray. For the case drawn, $\angle i=45^{\circ }$ and $\angle e=52.4^{\circ }$ with $\angle A=60^{\circ }$, so $\angle D=\angle i+\angle e-\angle A=37.4^{\circ }$.

    Step-by-step solution →
12. Q112 CBSE 2025
    Define the term 'power of accommodation' of human ​eye. Write the name of the part of eye ​which plays ​a major role in this process and ​explain what happens when the ​human eye focuses

    1. (i)on ​nearby objects, and
    2. (ii)on distant objects.
    Show answer

    Power of accommodation is the eye lens's ability to change its focal length; ciliary muscles contract for near objects and relax for distant ones.

    The power of accommodation of the human eye is the ability of the eye lens to adjust its own focal length, by changing its curvature, so that the images of objects lying at different distances are always formed sharply on the retina. The part of the eye that plays the major role is the **ciliary muscle**, which acts on the flexible eye lens through the suspensory ligaments. (i) On a **nearby** object: the ciliary muscles contract, the tension in the suspensory ligaments is released, the eye lens becomes thicker and more curved, its focal length decreases (its power increases), and the strongly diverging rays from the near object are converged on to the retina. Taking the retina at $v=2.5$ cm and the near point at $u=-25$ cm, $\frac{1}{f}=\frac{1}{2.5}+\frac{1}{25}$, so $f=2.27$ cm ($P=44$ D). (ii) On a **distant** object: the ciliary muscles relax, the suspensory ligaments become taut, the eye lens becomes thinner and less curved, its focal length increases (its power decreases), and the nearly parallel rays from the distant object are focused on the retina. With $u$ at infinity, $f=v=2.5$ cm ($P=40$ D).

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13. Q113 CBSE 2025
    A person ​has ​to keep reading material ​much beyond 25 cm (say at ​50 cm) from the eye for comfortable reading. Name the defect ​of vision he is suffering from. List two causes responsible ​for arising of this defect. Draw ​a labelled diagram showing correction ​of this defect using eye-glasses. Are these glasses convergent or divergent of light ?
    Show answer

    Hypermetropia; caused by a long eye-lens focal length or a small eyeball; corrected by convergent convex glasses, $f=+50$ cm.

    The defect is hypermetropia (far-sightedness): the near point has moved from 25 cm to about 50 cm. Two causes: (i) the focal length of the eye lens is too long; (ii) the eyeball has become too small. It is corrected with spectacles having convex lenses, which form the image of print held at 25 cm at the eye's near point, 50 cm away, as in the labelled diagram (here $f=+50$ cm, $P=+2$ D). The glasses are convergent.

    Step-by-step solution →
14. Q114 CBSE 2025
    A person ​is suffering from an ​eye ​defect in which the far point of the eye is much nearer than ​infinity. ​Name the defect of vision the ​person is suffering ​from. List two ​main causes of this defect. Write the type of the corrective lens and draw a ray diagram to show the function of the corrective lens.
    Show answer

    Myopia, caused by excessive lens curvature or an elongated eyeball, is corrected by a concave lens.

    The person has myopia (near-sightedness): distant objects cannot be seen clearly because their image is formed in front of the retina. Two main causes: (i) excessive curvature of the eye lens; (ii) elongation of the eyeball. It is corrected with a concave (diverging) lens of suitable power. Ray diagram: parallel rays from a distant object pass through the concave lens and diverge as if they came from the far point F of the eye; the eye lens then focuses them on the retina, so the image is formed on the retina.

    Step-by-step solution →
15. Q115 CBSE 2025
    A ​person uses lenses of $+2.0$ D power in his ​spectacles for the correction of ​his vision.

    1. (a)Name ​the defect of vision the person is suffering ​from.
    2. (b)List ​two causes of ​this defect.
    3. (c)Determine the focal length of the lenses used in the spectacles.
    Show answer

    The person has hypermetropia, since $+2.0$ D is a convex lens; $f=+50$ cm.

    (a) Hypermetropia, that is far-sightedness or long-sightedness, since a positive power means a convex, converging lens. (b) Two causes: the converging power of the eye lens has become too small, that is its focal length is too long; and the eyeball has become too short, so the eye lens sits too close to the retina. In either case the image of a near object falls behind the retina. (c) $f=\frac{1}{P}=\frac{1}{+2.0\text{D}}=+0.5$ m $=+50$ cm.

    Step-by-step solution →
16. Q116 CBSE 2025
    A ​person ​uses ​lenses of power $-0.5$ D in his ​spectacles for the correction of his vision.

    1. (a)Name the defect of vision the person is suffering from.
    2. (b)List ​two ​causes of this defect.
    3. (c)Determine the focal length ​of the lenses used in the ​spectacles.
    Show answer

    The person has myopia, since $-0.5$ D is a concave lens; $f=-2$ m $=-200$ cm.

    (a) Myopia, that is near-sightedness: a negative power means a concave, diverging lens. (b) Two causes: excessive curvature of the eye lens, and elongation of the eyeball. In either case the image of a distant object is formed in front of the retina. (c) $f=\frac{1}{P}=\frac{1}{-0.5\text{D}}=-2$ m $=-200$ cm.

    Step-by-step solution →
17. Q117 CBSE 2025
    1. (a)Draw a diagram to show the dispersion of ​white ​light by a glass ​prism.
    2. (b)What is ​spectrum ? Give reason ​for its formation.
    Show answer

    A prism splits white light into a spectrum of seven colours, because different colours bend through different angles, red least and violet most.

    (a) The diagram shows a narrow beam of white light falling on one face of a glass prism, splitting into colours inside the prism, and leaving as separate coloured rays bent towards the base, which form a band on a screen with red at the top and violet at the bottom. (b) The band of the coloured components of a light beam is called its spectrum; for white light it is violet, indigo, blue, green, yellow, orange and red (VIBGYOR). It forms because different colours of light bend through different angles as they pass through the prism — red the least and violet the most — since the refractive index of glass is different for different colours; each colour emerges along a different path, and so the colours become distinct.

    Step-by-step solution →
18. Q118 CBSE 2023
    What is ​a rainbow ​? ​Draw ​a labelled ​diagram to ​show its formation.
    Show answer

    A rainbow is a natural spectrum in the sky after rain, formed by dispersion of sunlight in water droplets, opposite to the Sun.

    A rainbow is a natural spectrum appearing in the sky after a rain shower. It is caused by the dispersion of sunlight by tiny water droplets in the atmosphere, and it is always formed in the direction opposite to the Sun. Formation: each droplet acts like a small prism. Sunlight entering it is refracted and dispersed into its colours, is reflected internally at the back of the drop, and is refracted again as it comes out. The colours leave at slightly different angles (red at about 42 degrees and violet at about 40 degrees to the incoming sunlight), so different colours reach the observer from droplets at different heights, with red on the outside of the bow and violet on the inside (see the labelled diagram).

    Step-by-step solution →
19. Q119 CBSE 2025
    1. (i)Define the term power of accommodation of human eye. What happens to the image ​distance in the eyes when the distance of an object is increased gradually from about $5$ m to $500$ m from our ​eyes ​? Name and explain the role of the part of human eye responsible for it in this case.
    2. (ii)A person ​is unable to see distinctly the objects placed beyond $2$ m from his eyes. Name the defect of vision the ​person is suffering from. List two possible causes of this defect and write the type of lenses used for the correction of this ​defect.
    Show answer

    Image distance stays constant as the ciliary muscles change the lens focal length; the person has myopia, corrected by a concave lens.

    (i) The power of accommodation of the human eye is the ability of the eye lens to adjust its focal length, by changing its curvature, so that objects at different distances are focused clearly on the retina. As the object is moved gradually from about $5$ m to about $500$ m, the image distance in the eye does not change: it remains constant, equal to the fixed distance between the eye lens and the retina, about $2.5$ cm, because the retina cannot move. The part responsible is the ciliary muscle. As the object recedes, the ciliary muscles relax, the eye lens becomes thinner, its curvature decreases and its focal length increases, so the image of the more distant object is still formed on the retina. (ii) The person has a far point of $2$ m instead of infinity, so he is suffering from myopia, that is short sightedness. Two possible causes are excessive curvature of the eye lens and elongation of the eyeball. The defect is corrected by using a concave, that is a diverging, lens of suitable power; here a lens of focal length $-2$ m, of power $-0.5$ D, would be required.

    Step-by-step solution →
20. Q120 CBSE 2025
    1. (i)​When and where does a rainbow ​appear in the sky ? List the phenomena of light which occur ​during ​the formation of a rainbow in proper sequence. Draw a labelled diagram to show the formation of a rainbow.
    2. (ii)List two conditions to observe a rainbow in the ​sky. Why can a rainbow not be seen ​from the surface of the moon ? ​Explain.
    Show answer

    Raindrops refract, internally reflect and refract sunlight to form a rainbow opposite the Sun; the Moon has no atmosphere, so none forms.

    (i) A rainbow appears in the sky after a rain shower, when the Sun is shining and tiny water droplets are still present in the air; it is always seen in the direction opposite to the Sun, with the Sun behind the observer. The phenomena in sequence: (1) refraction of sunlight as it enters a raindrop, with dispersion into its colours; (2) internal reflection at the back surface of the drop; (3) refraction again as the light leaves the drop, which disperses the colours further. The labelled diagram shows a raindrop with white sunlight entering it, the points of refraction and dispersion, internal reflection and final refraction marked, and the red and violet rays emerging towards the observer. (ii) Conditions: (1) the Sun must be shining behind the observer and fairly low in the sky; (2) there must be water droplets in the air in front of the observer, opposite the Sun, as after rain or near a waterfall or fountain. A rainbow cannot be seen from the surface of the Moon because the Moon has practically no atmosphere: there are no water droplets above its surface to refract, disperse and internally reflect sunlight.

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