Question Bank — The Human Eye and the Colourful World

NCERT Class 10 Science · Chapter 10 · CBSE Board Pattern

Class 10 Science Chapter 10 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

  1. The part of the human eye that controls the amount of light entering it is the
    (a) cornea (b) iris (c) retina (d) ciliary muscles

  2. A person can see distant objects clearly but has difficulty reading a book held at 25 cm. This defect is
    (a) myopia (b) hypermetropia (c) presbyopia (d) cataract

  3. When white light passes through a glass prism, the colour that bends the most is
    (a) red (b) yellow (c) green (d) violet

  4. The phenomenon responsible for the reddish appearance of the Sun at sunrise and sunset is
    (a) dispersion (b) atmospheric refraction (c) scattering (d) total internal reflection

  5. The least distance of distinct vision for a young adult with normal vision is approximately
    (a) 10 cm (b) 25 cm (c) 50 cm (d) infinity

Assertion-Reason Questions

  1. Assertion (A): The sky appears blue to an observer on the Earth’s surface.
    Reason (R): Fine particles in the atmosphere scatter shorter wavelengths of light more effectively than longer wavelengths.
    (a) Both A and R are true and R is the correct explanation of A
    (b) Both A and R are true but R is not the correct explanation of A
    (c) A is true but R is false
    (d) A is false but R is true

  2. Assertion (A): Planets do not twinkle while stars do.
    Reason (R): Planets are much closer to the Earth and appear as extended sources of light.
    (a) Both A and R are true and R is the correct explanation of A
    (b) Both A and R are true but R is not the correct explanation of A
    (c) A is true but R is false
    (d) A is false but R is true

  3. The crystalline lens of the eye changes its focal length with the help of
    (a) pupil (b) retina (c) ciliary muscles (d) optic nerve

  4. In the dispersion of white light by a prism, the sequence of colours observed is
    (a) VIBGYOR (b) ROYGBIV (c) VIBGYOR reversed (d) random order

  5. The Tyndall effect is observed when a beam of light passes through
    (a) a true solution (b) a colloidal suspension (c) pure water (d) vacuum

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Define the term ‘power of accommodation’ of the human eye.
  2. What is the far point of a normal human eye? State its value.
  3. A myopic person cannot see objects beyond 2 m clearly. Name the type of lens required to correct this defect and state one reason why the defect occurs.
  4. What is meant by the dispersion of light? Give one natural example.
  5. Why does the sky appear dark to an astronaut in space?
  6. State two conditions under which the Tyndall effect can be observed in daily life.

Section C — Short Answer (5 questions, 3 marks each)

  1. Draw a neat labelled diagram of the human eye and mark the following parts: cornea, iris, pupil, lens and retina. State the function of the retina.
  2. With the help of a ray diagram, show how a hypermetropic eye forms the image of a nearby object. Mention two possible causes of this defect.
  3. Explain, with a labelled diagram, the refraction of a ray of light through a triangular glass prism. Mark the angle of incidence, angle of refraction, angle of emergence and angle of deviation.
  4. What is presbyopia? How is it corrected? Why do some people need bifocal lenses?
  5. Differentiate between the apparent position and the actual position of a star as seen from the Earth. Why does this difference occur?

Section D — Long Answer (3 questions, 5 marks each)

  1. (Diagram-based) Draw a labelled diagram showing the dispersion of white light by a glass prism. Explain why the colours separate and why violet deviates the most while red deviates the least. How did Newton confirm that sunlight consists of seven colours?

  2. Explain, with suitable ray diagrams, how myopia and hypermetropia are corrected using appropriate lenses. State the position of the image in each defective eye before correction.

  3. Describe the formation of a rainbow with a labelled diagram. Explain the role of refraction, dispersion and internal reflection in the process. Why is a rainbow always formed in a direction opposite to the Sun?

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

After a rain shower, a student observes a rainbow in the sky opposite to the direction of the Sun. The teacher explains that tiny water droplets in the atmosphere act like prisms.

25.1 What optical phenomenon causes the splitting of sunlight into colours inside each raindrop?
25.2 Which two processes inside the raindrop are responsible for the observer seeing the rainbow?
25.3 Why does the rainbow appear in a direction opposite to the Sun?
25.4 Name the sequence of colours observed in the rainbow (use VIBGYOR).

Case 2

A person notices that the Sun becomes visible about two minutes before the actual sunrise and remains visible two minutes after the actual sunset. The teacher attributes this to atmospheric refraction.

26.1 Define atmospheric refraction.
26.2 Why does the Sun appear flattened at sunrise and sunset?
26.3 How does the gradual change in refractive index of air layers cause the apparent advance of sunrise?
26.4 Would this effect be observed if the Earth had no atmosphere? Justify.

Section F — HOTS and Application (4 questions, 3 marks each)

  1. Predict-and-justify: What would happen to the colour of the sky if the Earth’s atmosphere had no fine particles or molecules capable of scattering light? Explain with reason.

  2. Analyse an anomalous observation: In an experiment, a beam of white light is passed through a glass prism and a spectrum is obtained on a screen. When the same prism is placed in an inverted position immediately after the first prism, a beam of white light emerges. Explain this observation.

  3. Apply to an unfamiliar real-life situation: A motorist driving through dense fog at night finds red rear lights of vehicles more visible from a distance than blue lights. Which property of light is responsible? Relate it to the size of scattering particles in fog.

  4. Compare two situations: A star is observed twinkling brightly near the horizon while a planet at the same position does not twinkle. Compare the two situations and justify why the outcomes differ.

▶ Answer Key Attempt all questions first,
then tap to reveal

Section A

  1. (b) iris
  2. (b) hypermetropia
  3. (d) violet
  4. (c) scattering
  5. (b) 25 cm
  6. (a)
  7. (a)
  8. (c) ciliary muscles
  9. (a) VIBGYOR
  10. (b) colloidal suspension

Section B

  1. Ability of eye lens to adjust focal length using ciliary muscles (1) to focus objects at different distances (1).
  2. Farthest point up to which eye sees clearly; infinity for normal eye (2).
  3. Concave lens (1); due to excessive curvature of eye lens or elongation of eyeball (1).
  4. Splitting of white light into component colours (1); rainbow (1).
  5. No atmosphere → no scattering of blue light (2).
  6. Sunlight through smoke-filled room; sunlight through forest canopy (any two, 1 each).

Section C

  1. Diagram with 5 parts labelled (2); retina converts light into electrical signals sent to brain (1).
  2. Ray diagram showing image behind retina (2); causes: long focal length of lens or small eyeball (1).
  3. Labelled diagram with i, r, e, D marked (2); explanation of bending at two surfaces (1).
  4. Loss of accommodation with age due to weakening ciliary muscles (1); bifocal lenses (concave upper, convex lower) (2).
  5. Star appears slightly higher due to atmospheric refraction (1); atmosphere has varying refractive index (1); position changes continuously (1).

Section D

  1. Diagram of dispersion (2); different wavelengths bend by different amounts, violet most (2); Newton’s recombination experiment (1).
  2. Two ray diagrams (myopia image in front of retina, corrected by concave lens; hypermetropia image behind retina, corrected by convex lens) (3); brief cause for each defect (2).
  3. Labelled diagram showing refraction, dispersion, internal reflection in raindrop (3); observer sees dispersed colours opposite Sun (2).

Section E

25.1 Dispersion (1)
25.2 Refraction and internal reflection (1)
25.3 Sunlight enters droplets from opposite side (1)
25.4 VIBGYOR (1)
26.1 Refraction by Earth’s atmosphere (1)
26.2 Varying density layers bend rays differently (1)
26.3 Successive refraction raises apparent position (1)
26.4 No (1)

Section F

  1. Sky would appear dark (1) because no scattering occurs (2).
  2. Second prism recombines dispersed colours back into white light (3).
  3. Scattering; larger fog particles scatter longer wavelengths (red) less, allowing red to travel farther (3).
  4. Stars are point sources → fluctuations visible (1.5); planets are extended sources → variations average out (1.5).
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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.