👁️‍🗨️ UNIT – 10: THE HUMAN EYE AND THE COLOURFUL WORLD(Question)

👁️‍🗨️ UNIT – 10: THE HUMAN EYE AND THE COLOURFUL WORLD

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I. Multiple Choice Questions (1 Mark each)

1️⃣ The area where the image is formed in the eye is
A) Cornea B) Retina C) Iris D) Lens

2️⃣ The part of the eye that forms an inverted real image of the object on the retina is
A) Eye lens B) Pupil C) Iris D) Cornea

3️⃣ The lens used to correct near-sightedness (myopia) is
A) Biconvex B) Plano-convex C) Concave D) None

4️⃣ In old age, the eye lens sometimes becomes cloudy and whitish. This condition is called
A) Hypermetropia B) Myopia C) Presbyopia D) Cataract

5️⃣ A person can see objects clearly between 40 cm and 80 cm only. The defect is
A) Near-sightedness and use concave lens
B) Far-sightedness and use convex lens
C) Presbyopia and use bifocal lens
D) Eye surgery

6️⃣ The structure that controls change in the focal length of the eye lens is
A) Ciliary muscles B) Eyelid C) Retina D) Iris

7️⃣ The Sun is visible two minutes before sunrise and after sunset because of
A) Refraction of light B) Reflection C) Scattering D) Dispersion

8️⃣ The colour of the sky seen from the Moon’s surface is
A) Blue B) Red C) Black D) Violet

9️⃣ The colour that bends the least in a glass prism is
A) Violet B) Blue C) Green D) Red

10️⃣ While viewing distant objects, which change occurs in the eye?
A) Focal length decreases
B) Lens curvature increases
C) Focal length increases
D) Ciliary muscles relax

11️⃣ The correct statement regarding scattering of light and particle size is
A) Small particles scatter red light
B) Large particles scatter blue light
C) Large particles scatter violet light
D) Very large particles scatter all colours equally

12️⃣ The nature of the image formed by the eye lens on the retina is
A) Real and inverted B) Virtual and upright C) Real and upright D) Virtual and inverted

13️⃣ The colour least scattered by fog and smoke is
A) Orange B) Blue C) Red D) Violet

14️⃣ Identify the wrong statement:
A) Stars twinkle
B) Sky appears blue to astronauts
C) Sun visible before sunrise
D) Planets do not twinkle

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II. One Mark Questions

15. What is the near point of the eye? State its value for a normal eye.

16. What is the far point of the eye? State its value for a normal eye.

17. What is the spectrum of white light?

18. What are the common defects of vision?

19. What is the angle of deviation?

20. What is the angle of a prism?

21. What is the emergent angle?

22. Name the parts of the eye for the following:
     a) Transparent bulge on front surface b) Dark muscular diaphragm

23. Identify the eye in the image and mention its remedy.

24. What is light dispersion?

25. Can rainbows be observed on the Moon? Why?

26. What are the near and far points of a person with normal vision?

27. Name two atmospheric phenomena caused by refraction.

28. What is accommodation of the eye?

29. What colour is used in danger signals and why?

30. A student cannot read the blackboard from the back bench. Identify the defect and its correction.

31. Identify the eye defect shown in the image and suggest a remedy.

32. What is the function of the pupil?

33. Observe the figure of refraction through a prism. Name the angle marked X and explain its formation.

34. What is cataract?

35. After light passes through a prism, name the least and most bent colours.

36. Three glass prisms A, B, and C are arranged together. Will a spectrum form on the screen? Explain.

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III. Two Mark Questions

37. What is hypermetropia? What are its causes?

38. What is myopia? What are its causes?

39. Explain the formation of a rainbow in nature.

40. Explain Newton’s experiment to show that white light contains seven colours.

41. Describe Newton’s recombination of white light experiment.

42. Write the differences between myopic and hypermetropic eyes.

43. Identify and justify the eye types shown: normal, near-sighted, and far-sighted.

44. A person buys spectacles with -2.0 D lenses. Which defect do they correct? Explain.

45. Explain how the human eye adjusts to view near and distant objects.

46. Identify the eye defect in the given figure.

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IV. Three Mark Questions

47. What is the Tyndall effect? Give two examples.

48. Why is the sky blue in colour? Explain.

49. Draw a diagram to show recombination of white light.

50. Why do stars twinkle but planets do not? Explain.

51. What is presbyopia? State its causes and remedy.

52. A doctor prescribes a lens with power –0.5 D. Find its focal length and type of lens.

53. a) Why can’t we see objects clearly closer than 25 cm?
     b) Explain the relationship between light scattering and particle size.

54. a) Why does sunlight appear white at noon?
     b) What is the working principle of the human eye?
     c) Write the function of: (i) Iris (ii) Pupil (iii) Cornea

55. A white light beam PQ passes through a prism.
     a) Name the phenomenon observed.
     b) Explain the reason for this phenomenon.

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V. Four Mark Questions

56. a) Explain the phenomenon of rainbow formation in the atmosphere.
     b) Why do stars twinkle?

57. a) Define myopia. Mention its causes.
     b) Explain the power of accommodation of the eye.

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👁️‍🗨️ UNIT – 10 : THE HUMAN EYE AND THE COLOURFUL WORLD – KEY ANSWERS

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I. Multiple Choice Questions (1 mark each)

Q.No	Correct Answer	Explanation
1	✅ B. Retina	Image forms on retina
2	✅ A. Eye lens	Forms real, inverted image on retina
3	✅ C. Concave	Corrects myopia (near-sightedness)
4	✅ D. Cataract	Lens becomes cloudy due to protein deposit
5	✅ A. Near-sightedness, use concave lens	Sees nearby objects clearly
6	✅ A. Ciliary muscles	Control curvature of lens
7	✅ A. Refraction of light	Bending of light makes sun visible early/late
8	✅ C. Black	No atmosphere → no scattering on Moon
9	✅ D. Red	Red light deviates least in prism
10	✅ D. Ciliary muscles relax	For distant vision, lens becomes thinner
11	✅ D. Very large particles scatter all colours equally	Explains white clouds and fog
12	✅ A. Real and inverted	Image on retina is real and inverted
13	✅ C. Red	Least scattered, used in fog lights/danger signals
14	✅ B. Sky appears blue to astronauts	False — space has no atmosphere

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II. One Mark Questions – Key Answers

15. Near point: The closest distance at which eye can see clearly — 25 cm for normal eye.

16. Far point: The farthest distance at which eye can see clearly — infinity for normal eye.

17. Spectrum: Band of seven colours obtained when white light disperses through a prism.

18. Defects of vision: Myopia, Hypermetropia, Presbyopia, Cataract.

19. Angle of deviation: Angle between incident ray and emergent ray in a prism.

20. Angle of prism: Angle between two refracting surfaces of a prism.

21. Emergent angle: Angle between emergent ray and normal at second surface of prism.

22. a) Cornea b) Iris

23. Eye defect: Myopia (short-sightedness) → corrected with concave lens.

24. Dispersion: Splitting of white light into its constituent colours.

25. No, because there is no atmosphere on the Moon for refraction or dispersion.

26. Near point: 25 cm Far point: Infinity.

27. Examples: Twinkling of stars, advance sunrise/delayed sunset.

28. Accommodation: Ability of eye to adjust focal length to see near and far objects.

29. Colour: Red — least scattered, visible from far, used in danger signals.

30. Defect: Myopia — corrected by concave lens.

31. Defect: Hypermetropia — corrected by convex lens.

32. Function of pupil: Regulates amount of light entering the eye.

33. Angle X: Angle of deviation — due to refraction through prism.

34. Cataract: Clouding of lens → partial/complete blindness (corrected by surgery).

35. Least bent: Red Most bent: Violet.

36. No spectrum forms — because white light recombines when prisms are arranged oppositely.

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III. Two Mark Questions – Key Answers

37. Hypermetropia: Far-sightedness — can’t see nearby objects.
    Causes: Short eyeball or lens less curved.

38. Myopia: Near-sightedness — can’t see distant objects.
    Causes: Elongated eyeball or lens too curved.

39. Rainbow formation: Dispersion + internal reflection + refraction of sunlight in water droplets.

40. Newton’s prism experiment: White light dispersed into seven colours through prism.

41. Recombination experiment: Two prisms restore dispersed light back to white light.

42. Differences:

Myopia	Hypermetropia
Distant object blurred	Near object blurred
Image before retina	Image behind retina
Concave lens	Convex lens

43. Eye types:

• Normal – image on retina

• Myopic – image before retina

• Hypermetropic – image behind retina

44. Lens power –2.0 D: Concave lens, corrects myopia.

45. Accommodation: Ciliary muscles adjust lens curvature for clear vision of near/far objects.

46. Eye defect: Presbyopia — corrected by bifocal lenses.

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IV. Three Mark Questions – Key Answers

47. Tyndall effect: Scattering of light by colloidal particles.
    Examples:
    (i) Blue colour of sky.
    (ii) Visibility of sun rays in a dark room through window.

48. Sky is blue: Molecules of air scatter shorter wavelengths (blue) more than longer ones.

49. Diagram: Recombination of white light showing VIBGYOR merging back to white.

50. Stars twinkle: Light refracted through varying air layers.
    Planets do not: Larger apparent size averages out twinkling.

51. Presbyopia: Due to loss of lens flexibility with age.
    Remedy: Bifocal lens (concave + convex).

52. Power = –0.5 D → F = –2 m → Concave lens (negative focal length).

a) Below 25 cm, lens cannot accommodate → image blurry.
b) Small particles scatter blue; larger scatter red.

a) Sunlight white at noon → least scattering.
b) Eye works on refraction of light by lens on retina.
c) Functions:
 i) Iris – controls pupil size
 ii) Pupil – regulates light entry
 iii) Cornea – refracts incoming light

a) Phenomenon: Dispersion.
b) Reason: Different colours have different refractive indices (V > R).

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V. Four Mark Questions – Key Answers

a) Rainbow formation: Sunlight refracted → internally reflected → dispersed → observer sees VIBGYOR.
b) Stars twinkle: Due to atmospheric refraction; light bends through moving air layers.

a) Myopia: Distant objects appear blurred; image before retina.
Causes: Long eyeball or high curvature of lens.
Correction: Concave lens.
b) Power of accommodation: Ability of ciliary muscles to change focal length for clear vision.

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