Skip to content

How does the focal length of… (Class 10 Science 2026, Q34a)

questionbuddy.in/q/cbse-10-science-2026-31-2-1-q34a-how-does-focal-length-eye

ScienceCBSE Class 10 · Board exam 2026, set 31/2/1 · 2 marks · Very short answer

CBSE Class 10 Science 2026: question 34(a)

Set in the CBSE Class 10 board exam of 2026, paper 31/2/1, section C, question 34(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q34(a) · 2 marks · Very short answerThe Human Eye and the Colourful World

How does the focal length of eye lens change as the distance of the object from the eyes is altered ? Explain.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/2/1.

Hints

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

Hint 1

Which muscles change the shape of the eye lens?

Hint 2

A thicker lens bends light more, so does it have a shorter or longer focal length?

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. When the object is moved farther from the eye, the ciliary muscles relax. The eye lens becomes thinner and its focal length increases, so a distant object is focused on the retina.

    1 mark

  2. When the object is brought closer to the eye, the ciliary muscles contract. The eye lens becomes thicker and its focal length decreases, so a near object is focused on the retina. This ability is called accommodation.

    1 mark

Answer: Farther object: ciliary muscles relax, lens thins, focal length increases; nearer object: muscles contract, lens thickens, focal length decreases.

Where the marks are

  • Distant object: ciliary muscles relax, lens thin, focal length increases (1 mark)
  • Near object: ciliary muscles contract, lens thick, focal length decreases (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 paper2026 board paper, set 31/2/1: 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.