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Study the diagram given below… (Class 10 Science 2024, Q31)

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ScienceCBSE Class 10 · Board exam 2024, set 31/1/1 · 3 marks · Short answer

CBSE Class 10 Science 2024: question 31

Set in the CBSE Class 10 board exam of 2024, paper 31/1/1, section C, question 31, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q31 · 3 marks · Short answerCompetency-basedThe Human Eye and the Colourful World

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.

Figure in the paper: Eye diagram: a point object N on the left on the principal axis, a point N′ closer to the eye. Light rays from N pass through the lens and converge to a point on the far side that lies behind the retina (shown by dashed lines extending beyond the retina), with arrows on the rays showing direction of travel toward the retina. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Where do the rays meet relative to the retina in the figure?

Hint 2

If the rays meet too far back, the eye needs extra converging power. Which lens provides it?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i) Defect: Hypermetropia (far-sightedness).

    ½ mark

  2. Reason: light from a nearby object (N′) is focused behind the retina, so the near point (N) lies farther than 25 cm.

    ½ mark

  3. (ii) Cause 1: the focal length of the eye lens is too long, so the lens is less converging.

    ½ mark

  4. Cause 2: the eyeball has become too small (shortened).

    ½ mark

  5. (iii) Correction diagram: place a convex lens of suitable power in front of the eye. Rays from the object at the normal near point N′ (25 cm) are made less divergent by the lens, so they appear to come from N. The eye lens then focuses them on the retina. Label N, N′, the convex lens, the retina and the arrows on the rays.

    1 mark

Answer: (i) Hypermetropia, since the image forms behind the retina; (ii) focal length too long, eyeball too small; (iii) corrected with a convex lens

Where the marks are

  • Names hypermetropia (½ mark)
  • Reason: image formed behind retina / near point farther than 25 cm (½ mark)
  • Two causes (½ + ½ marks)
  • Labelled diagram of correction with a convex lens (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from The Human Eye and the Colourful World, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.