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State reasons for Myopia… (Class 10 Science 2023, Q31)

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ScienceCBSE Class 10 · Board exam 2023, set 31/6/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 31

Set in the CBSE Class 10 board exam of 2023, paper 31/6/1, section C, question 31, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q31 · 3 marks · Short answerThe Human Eye and the Colourful World

State reasons for Myopia. With the help of ray diagrams, show the
(a) image formation by a myopic eye, and
(b) correction of myopia using an appropriate lens.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/6/1.

Hints

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

Hint 1

In myopia, distant objects are blurred. Where does the image fall relative to the retina?

Hint 2

To push the image back onto the retina, the rays must be spread out first. Which lens does that?

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. Reason 1: excessive curvature of the eye lens (focal length too short).

    ½ mark

  2. Reason 2: elongation of the eyeball (distance between lens and retina too large).

    ½ mark

  3. (a) Diagram (in words): Draw parallel rays from a distant object entering the eye lens. They meet at a point in front of the retina, so the image of a distant object is blurred. Mark the far point and the arrows on the rays.

    1 mark

  4. (b) Diagram (in words): Place a concave (diverging) lens of suitable power in front of the eye. The parallel rays are first diverged, so they appear to come from the far point. The eye lens then focuses them on the retina. Mark the arrows on the rays.

    1 mark

Answer: Causes: excessive curvature of eye lens, elongated eyeball. Image forms in front of the retina; corrected by a concave lens.

Where the marks are

  • Excessive curvature of eye lens (½ mark)
  • Elongation of eyeball (½ mark)
  • Ray diagram showing image in front of retina (1 mark)
  • Ray diagram of correction with concave lens, image on retina (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 paper2023 board paper, set 31/6/1: 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.