Chapter 10: The Human Eye and the Colourful World

Important questions — the ones the board asked most (20)

1. Q1Long answer5 marksAsked: 2025

   (a) (i) The power of a lens 'X' is - 2.5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ? (ii) "The value of magnification 'm' for a lens is - 2." Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state : (I) the nature of the image formed; (II) size of the image compared to the size of the object; (III) position of the image, and (IV) sign of the height of the image. (iii) The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence ? Give reason to justify your answer. OR (b) (i) Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass. (ii) State Snell's law of refraction of light. (iii) Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of : (I) object distance, and (II) magnification.

   

   Medha Ma’am

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   Model answer · Power of lens, magnification

   1. 1.(a)(i) The power is negative, so X is a concave (diverging) lens; it is prescribed to correct myopia (near-sightedness). OR (b)(i) Ray diagram: the ray falling obliquely from air enters the glass slab and bends towards the normal.1 mark
   2. 2.f = 1/P = 1/(−2.5) m = −0.4 m = −40 cm. OR The emergent ray comes out parallel to the incident ray, displaced sideways; normals at both faces and angles i, r, e marked.1 mark
   3. 3.(a)(ii)(I), (II) As m = −2, the image is real and inverted, and twice the size of the object. OR (b)(ii) Snell's law: for light of a given colour and a given pair of media, sin i / sin r is constant (= n₂₁).1 mark
   4. 4.(III), (IV) u = −20 cm, so v = m × u = (−2)(−20) = +40 cm: the image is 40 cm on the other side of the lens, and its height is negative. OR (b)(iii)(I) A convex lens forms a virtual image only when the object is between F and the optical centre; a concave lens forms one for every object position.1 mark
   5. 5.(a)(iii) Lens A (10 cm): P = 1/f, so the shorter focal length gives the greater power (A 10 D, B 5 D) and the greater convergence or divergence. OR (b)(iii)(II) The virtual image of a convex lens is magnified (m > 1); that of a concave lens is diminished (m < 1).1 mark

   Marks split from a structure derived from past papers (checked twice); not CBSE’s official scheme

2. Q2Long answer5 marksAsked: 2025

   (a) (i) The power of a lens 'X' is – 2.5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ? (ii) "The value of magnification 'm' for a lens is – 2." Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state : (I) the nature of the image formed; (II) size of the image compared to the size of the object; (III) position of the image, and (IV) sign of the height of the image. (iii) The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence ? Give reason to justify your answer. OR (b) (i) Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass. (ii) State Snell's law of refraction of light. (iii) Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of : (I) object distance, and (II) magnification.

   

   Medha Ma’am

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   Hear it from Medha Ma’am · 210 s

   Model answer · Power of lens, magnification

   1. 1.(a)(i) Lens X is a concave (diverging) lens. OR (b)(i) Ray diagram: the ray falling obliquely from air on the first face bends towards the normal as it enters the glass.0.5 marks
   2. 2.f = 1/P = 1/(−2.5) m = −0.4 m = −40 cm. OR At the second face it bends away from the normal and emerges parallel to the incident ray (lateral displacement).1 mark
   3. 3.It is prescribed to correct myopia (near-sightedness). OR The normals, the angles i, r and e, and the incident, refracted and emergent rays are labelled.0.5 marks
   4. 4.(a)(ii)(I) m is negative, so the image is real and inverted. OR (b)(ii) Snell's law: sin i / sin r is constant,0.5 marks
   5. 5.(II) The image is twice the size of the object. OR — the constant being the refractive index of the second medium with respect to the first (n₂₁), for light of a given colour and a given pair of media.0.5 marks
   6. 6.(III) u = −20 cm and m = v/u = −2, so v = +40 cm: the image is 40 cm on the other side of the lens. OR (b)(iii)(I) A convex lens forms a virtual image only when the object is between F and the optical centre (closer than f).0.5 marks
   7. 7.(IV) The height of the image is negative. OR A concave lens forms a virtual image for any object distance.0.5 marks
   8. 8.(a)(iii) Lens A: P = 1/f, so the shorter focal length gives the greater power (P_A = 10 D, P_B = 5 D) and the greater convergence or divergence. OR (b)(iii)(II) The virtual image of a convex lens is magnified (m > 1); that of a concave lens is diminished (m < 1).1 mark

   Marks split from a structure derived from past papers (checked twice); not CBSE’s official scheme

3. Q3Case-based4 marksAsked: 2025

   In a class, students took a thick cardboard sheet and made a small hole at its centre. They allowed sunlight to fall on this small hole and obtained a thin beam of white light. Then they took a glass prism and allowed this white light to fall on one of its faces. Then they slowly rotated this prism until the light emerging from the opposite face of the prism began to fall on a screen placed nearby. They studied this beautiful band of light on the screen and concluded that this is the spectrum of white light. (i) Mention one other event where this same type of spectrum is observed. (ii) What happens to the white light in the above situation? (iii) (A) List two conditions necessary for observing a rainbow. Or (iii) (B) Draw a ray diagram to show the formation of a rainbow. On this diagram, mark (a), (b) and (c) as given below: (a) where dispersion of light takes place. (b) where internal reflection of light takes place. (c) where final refraction of light takes place.

   

   Medha Ma’am

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   Model answer · dispersion and rainbow

   1. 1.(i) A rainbow in the sky after a rain shower.1 mark
   2. 2.(ii) The prism splits the white light into its seven colours (VIBGYOR) — dispersion — because different colours bend through different angles.1 mark
   3. 3.(iii)(A) The Sun must be behind the observer. OR (iii)(B) Ray diagram of a water droplet: refraction with dispersion of white light where it enters, internal reflection at the back surface, and refraction again where it comes out.1 mark
   4. 4.Tiny water droplets must be present in the air in front of the observer (as after rain). OR Marked: (a) dispersion where light enters the drop, (b) internal reflection at the back surface, (c) final refraction where light leaves.1 mark

   Marks split from a structure derived from past papers (checked twice); not CBSE’s official scheme

4. Q4Case-based4 marksAsked: 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. (a) Name the phenomenon due to which a prism splits the incident white light into a band of colours. (b) State the reason of getting a band of seven colours in the above case. (c) (i) Explain with the help of a labelled ray diagram, an experimental arrangement to show the recombination of the spectrum of white light. OR (c) (ii) Draw a labelled ray diagram to show the formation of a rainbow.

5. Q5Short answer3 marksAsked: 2024

   31. (a) Define the term power of accommodation of human eye. Write the name of the part of eye which plays a major role in the process of accommodation and explain what happens when human eye focuses (i) nearby objects and (ii) distant objects. OR (b) Draw a ray diagram to show the formation of a rainbow in the sky. On this diagram mark A - where dispersion of light occurs, B - where internal reflection of light occurs and C - where refraction of light occurs. List two necessary conditions to observe a rainbow.

   How the model answer begins

   1. The power of accommodation of the human eye is the ability of the eye lens to adjust its focal length. Because of it, the eye can see both nearby and distant objects clearly.

   The full answer from Medha Ma’am →
6. Q6Short answer3 marksAsked: 2023

   Give reasons for the following : (a) Danger signals installed at airports and at the top of tall buildings are of red colour. (b) The sky appears dark to the passengers flying at very high altitudes. (c) The path of a beam of light passing through a colloidal solution is visible.

   How the model answer begins

   1. Danger signals installed at airports and at the top of tall buildings are of red colour because the red light has a wavelength about 1.8 times greater than blue light, that is, red has the longest wavelength among the…

   The full answer from Medha Ma’am →
7. Q7Short answer3 marksAsked: 2026

   37. (a) What is Tyndall effect? (b) What happens when sunlight is scattered from the particles of very large size? (c) 'Danger' signals are always red in colour. Why?

   How the model answer begins

   1. The phenomenon of scattering of light by the colloidal particles gives rise to Tyndall effect. When a beam of light strikes fine particles such as smoke, tiny water droplets and suspended particles of dust present in a…

   The full answer from Medha Ma’am →
8. Q8Short answer3 marksAsked: 2026

   Study the given diagram and answer the questions that follow : (a) Write the name of the eye defect shown in the diagram. Where is the image formed in this eye defect with respect to the retina of the eye ? (b) List two causes of this eye defect. (c) With the help of a diagram, show how this eye defect of vision is corrected.

   How the model answer begins

   1. The defect shown is hypermetropia (far-sightedness).

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9. Q9Short answer3 marksAsked: 2026

   Study the given diagram and answer the questions that follow : (a) Write the name of the eye defect shown in the diagram. Where is the image formed in this eye defect with respect to the retina of the eye ? (b) List two causes of this eye defect. (c) With the help of a ray diagram, show how this defect of vision is corrected.

   How the model answer begins

   1. (a) The defect of vision shown is myopia, also known as near-sightedness. The person can see nearby objects clearly but cannot see distant objects distinctly.

   The full answer from Medha Ma’am →
10. Q10Short answer3 marksAsked: 2026

    Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your explanation.

    How the model answer begins

    1. A rainbow is formed by the refraction, internal reflection and refraction again of sunlight by tiny water droplets in the atmosphere after rain.

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11. Q11Short answer3 marksAsked: 2025

    A person uses lenses of +2.0 D power in his spectacles for the correction of his vision. (a) Name the defect of vision the person is suffering from. (b) List two causes of this defect. (c) Determine the focal length of the lenses used in the spectacles.

12. Q12Short answer3 marksAsked: 2025

    (a) Draw a diagram to show the dispersion of white light by a glass prism. (b) What is a spectrum ? Write the cause of its formation.

    How the model answer begins

    1. (a) In the diagram, a narrow beam of white light falls on one face of a triangular glass prism. The light comes out of the other face as a band of colours on a screen. The colours are, in order, Violet, Indigo, Blue,…

    The full answer from Medha Ma’am →
13. Q13Short answer3 marksAsked: 2025

    A person uses lenses of power -0.5 D in his spectacles for the correction of his vision. (a) Name the defect of vision the person is suffering from. (b) List two causes of this defect. (c) Determine the focal length of the lenses used in the spectacles.

    How the model answer begins

    1. (a) The person is suffering from myopia (near-sightedness).

    The full answer from Medha Ma’am →
14. Q14Short answer3 marksAsked: 2024

    Study the diagram given below and answer the questions that follow : (i) Name the defect of vision represented in the diagram. Give reason for your answer. (ii) List two causes of this defect. (iii) With the help of a diagram show how this defect of vision is corrected.

    How the model answer begins

    1. The defect is hypermetropia (far-sightedness). Reason: the rays from a nearby object at N′ meet at a point behind the retina, so the image is formed behind the retina; the near point of the eye has moved farther away,…

    The full answer from Medha Ma’am →
15. Q15Short answer3 marksAsked: 2024

    31. Define the term power of accommodation of human eye. What happens to the image distance in the eye when we increase the distance of an object from the eye ? Name and explain the role of the part of human eye responsible for it in this case.

16. Q16Short answer3 marksAsked: 2026

    A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.

    How the model answer begins

    1. The person is suffering from hypermetropia, which is also known as far-sightedness.

    The full answer from Medha Ma’am →
17. Q17Short answer3 marksAsked: 2026

    What is scattering of light ? How is scattering of light different from reflection of light ? Explain.

    How the model answer begins

    1. Scattering of light happens when light passes through a medium that contains fine particles, such as dust, smoke, tiny water droplets or molecules of air. The particles spread the light in all directions, and this is…

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18. Q18Short answer3 marksAsked: 2026

    (a) Draw the ray diagram for refraction of light through a glass prism and mark angle of refraction and angle of deviation. (b) When the path of a light ray refracted through a glass prism is reversed how will the angle of deviation change ? Explain.

    How the model answer begins

    1. (a) In the ray diagram, a triangular glass prism ABC has refracting surfaces AB and AC. The incident ray PE falls on surface AB at point E. It goes from air to glass, so it bends towards the normal and travels as the…

    The full answer from Medha Ma’am →
19. Q19Short answer3 marksAsked: 2025

    What is a rainbow ? Draw a labelled diagram to show its formation.

20. Q20Short answer3 marksAsked: 2025

    31. A person has to keep the reading material at a distance much larger than 25 cm from his eyes (assume 50 cm) to read comfortably. Name the defect of vision he is suffering from. List two reasons due to which this defect arises. Draw a labelled diagram to show the correction of this defect by using lenses. Are these lenses converging or diverging ?

    How the model answer begins

    1. The person suffers from hypermetropia (far-sightedness). His near point is about 50 cm, which is farther away than the normal near point of 25 cm.

    The full answer from Medha Ma’am →

15 more questions of this chapter, each with its model answer, in the AskMedha app.

Objective questions with the board’s key (10)

1. 1. CBSE 2026

   30. When you look at an object very close to your eyes, the :

   • (A) Ciliary muscles of your eye contract and the eye lens becomes thick. ✓
   • (B) Ciliary muscles of your eye get relaxed and the eye lens becomes thick.
   • (C) Ciliary muscles of your eye contract and the eye lens becomes thin.
   • (D) Ciliary muscles of your eye get relaxed and the eye lens becomes thin.

   Answer: (A)

2. 2. CBSE 2026

   32. Assertion (A) : When rays of white light pass through a prism, on emerging they give spectrum of seven colours. Reason (R) : It is due to the scattering of light that red light bends minimum and violet light bends the maximum.

   • (A) Both, Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   • (B) Both, Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   • (C) Assertion (A) is true, but Reason (R) is false. ✓
   • (D) Assertion (A) is false, but Reason (R) is true.

   Answer: (C)

3. 3. CBSE 2026

   Observe the given ray diagram showing refraction through a prism and select the correct option for the colours of ray 1 and ray 2 :

   • (A) Blue, Red
   • (B) Green, Yellow
   • (C) Red, Violet ✓
   • (D) Violet, Red

   Answer: (C)

4. 4. CBSE 2026

   Observe the given ray diagram showing refraction through a prism and select the correct option for the colour of ray 1 and 2 :

   • (A) Blue, Red
   • (B) Green, Yellow
   • (C) Red, Violet ✓
   • (D) Violet, Red

   Answer: (C)

5. 5. CBSE 2026

   30. The pair of eye parts responsible for admitting different amount of light in to the eyes is

   • (A) Iris and pupil ✓
   • (B) Ciliary muscles and pupil
   • (C) Retina and Iris
   • (D) Ciliary muscles and cornea

   Answer: (A)

6. 6. CBSE 2026

   31. The vision defect which arises due to gradual weakening of the ciliary muscles and diminishing flexibility of eye lens is :

   • (A) Myopia
   • (B) Hypermetropia
   • (C) Presbyopia ✓
   • (D) Myopia and hypermetropia both

   Answer: (C)

7. 7. CBSE 2026

   Directions : For question number 32, two statements are given, one labelled as Assertion (A) and the other is labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below : Assertion (A) : When rays of white light pass through a prism, on emerging they give spectrum of seven colours. Reason (R) : It is due to the scattering of light that red light bends minimum and violet light bends the maximum.

   • (A) Both, Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   • (B) Both, Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   • (C) Assertion (A) is true, but Reason (R) is false. ✓
   • (D) Assertion (A) is false, but Reason (R) is true.

   Answer: (C)

8. 8. CBSE 2026

   A thin beam of white light falls on a face of a glass prism and a spectrum is obtained on a screen. Which of the following options is the correct sequence of colours from top to bottom on the screen ?

   • (A) Red, Green, Yellow, Violet, Blue
   • (B) Red, Yellow, Green, Blue, Violet ✓
   • (C) Violet, Blue, Green, Yellow, Red
   • (D) Violet, Red, Green, Yellow, Blue

   Answer: (B)

9. 9. CBSE 2026

   To restore clear vision in persons whose size of the eye ball has reduced, he/she is suggested to use suitable

   • (A) Converging lens ✓
   • (B) Diverging lens
   • (C) Bifocal lens
   • (D) Cylindrical lens

   Answer: (A)

10. 10. CBSE 2025

    Assertion (A): When ciliary muscles contract, the eye lens becomes thin. Reason (R): Ciliary muscles control the power of the eye lens.

    • (A) Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
    • (B) Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
    • (C) Assertion (A) is true but Reason (R) is false.
    • (D) Assertion (A) is false but Reason (R) is true. ✓

    Answer: (D)

Questions parents and students ask

How many marks does "The Human Eye and the Colourful World" carry in CBSE Class 10 Science?

In the CBSE papers of 2023–2026, this chapter carried about 5 marks and about 3 questions a year; by marks it ranks 11 in Science.

Which are the most important (VVI) questions of "The Human Eye and the Colourful World"?

The 20 questions above are from the board’s real papers, each with the years it was asked; the most-asked come first with their full model answers. All 35 written questions of this chapter, with answers, are in the AskMedha app.

Do the answers follow the board’s marking scheme?

Yes. CBSE publishes its marking schemes; every model answer here is written point by point to the marks the board’s own scheme gives, and checked by a second, independent model.