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Observe the following diagram… (Class 10 Science 2023, Q25)

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ScienceCBSE Class 10 · Board exam 2023, set 31/5/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 25

Set in the CBSE Class 10 board exam of 2023, paper 31/5/1, section B, question 25, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 2 marks · Very short answerCompetency-basedThe Human Eye and the Colourful World

Observe the following diagram showing an image formation in an eye :

  1. (a)

    Identify the defect of vision shown in the figure.

    0 marks
  2. (b)

    List its two causes and suggest a suitable corrective lens to overcome this defect.

    0 marks

Figure in the paper: A horizontal eyeball with a crystalline lens. Three parallel rays from a distant object on the left, from a point on the principal axis, are shown being refracted by the lens; the refracted rays converge at a point on the axis which lies beyond the retina (to the right), shown with dashed lines extended back to meet at that point behind the retina. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/5/1.

Hints

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

Hint 1

Where do the rays meet: in front of, on, or behind the retina?

Hint 2

An image formed behind the retina needs the rays to be converged more. 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. (a) The image is formed behind the retina, so the defect is hypermetropia (far-sightedness).

    ½ mark

  2. (b) Cause 1: the focal length of the eye lens is too long.

    ½ mark

  3. Cause 2: the eyeball has become too small (too short).

    ½ mark

  4. Correction: a convex (converging) lens of suitable power, which brings the image back onto the retina.

    ½ mark

Answer: (a) Hypermetropia; (b) focal length of eye lens too long, eyeball too small; corrected with a convex lens

Where the marks are

  • Identifies hypermetropia (½ mark)
  • Cause: focal length of eye lens too long (½ mark)
  • Cause: eyeball too small (½ mark)
  • Corrective lens: convex/converging (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 31/5/1: 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.