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Name the type of lenses… (Class 10 Science 2025, Q25B)

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ScienceCBSE Class 10 · Board exam 2025, set 31/4/1 · 2 marks · Very short answer

CBSE Class 10 Science 2025: question 25(B)

Set in the CBSE Class 10 board exam of 2025, paper 31/4/1, section B, question 25(B), for 2 marks. Try it first; the hints and our step-by-step solution are below.

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

Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/4/1.

Hints

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

Hint 1

Presbyopia often comes with difficulty in seeing both near and far objects.

Hint 2

Which lens corrects distant vision and which corrects near vision? Where on the lens would each part be useful?

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. Persons with presbyopia often have both myopia and hypermetropia. They need bifocal lenses.

    ½ mark

  2. Structure: the upper portion of a bifocal lens is a concave lens and the lower portion is a convex lens.

    1 mark

  3. Reason: the upper concave part helps in seeing distant objects, and the lower convex part helps in seeing nearby objects, for example while reading. (If only near vision is affected, a convex lens is used.)

    ½ mark

Answer: Bifocal lenses: concave upper part for distant vision and convex lower part for near vision.

Where the marks are

  • Names bifocal lenses, or a convex lens (½ mark)
  • Describes the structure: concave upper part and convex lower part, or a convex lens thicker at the middle (1 mark)
  • Gives the reason: distant and near vision respectively, or near vision for a convex 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 paper2025 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.