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Observe the following… (Class 10 Science 2023, Q25A)

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ScienceCBSE Class 10 · Board exam 2023, set 31/4/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 25(A)

Set in the CBSE Class 10 board exam of 2023, paper 31/4/1, section B, question 25(A), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q25(A) · 2 marks · Very short answerThe Human Eye and the Colourful World

Observe the following diagram and answer the questions following it :

  1. (i)

    Identify the defect of vision shown.

    ½ mark
  2. (ii)

    List its two causes.

    1 mark
  3. (iii)

    Name the type of lens used for the correction of this defect.

    ½ mark

Figure in the paper: Eye diagram: parallel light rays from the left (dashed extensions) enter the eye ball through the eye lens; the rays converge at a point in front of the retina, which is labelled 'Retina' on the right. Labels: 'Light rays' (left), 'Eye lens' (below the lens), 'Eye ball' (below the eyeball). See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/4/1.

Hints

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

Hint 1

Where is the image formed relative to the retina in the diagram?

Hint 2

An image in front of the retina means the eye converges light too much or the eyeball is too long.

Hint 3

To push the image back onto the retina, should the lens converge or diverge light?

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) The parallel rays from a distant object meet in front of the retina, so the defect is myopia (short-sightedness).

    ½ mark

  2. (ii) Causes:
    1. Excessive curvature of the eye lens.
    2. Elongation of the eyeball.

    1 mark

  3. (iii) It is corrected with a concave (diverging) lens of suitable power.

    ½ mark

Answer: (i) Myopia; (ii) Excessive curvature of eye lens, elongated eyeball; (iii) Concave lens

Where the marks are

  • Identifies myopia (½ mark)
  • Excessive curvature of eye lens (½ mark)
  • Elongation of eyeball (½ mark)
  • Concave / diverging lens (½ 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 31/4/1: 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.