Skip to content

A student wants to… (Class 10 Science SQP 2026-27, Q30)

questionbuddy.in/q/cbse-10-science-2026-27-sqp-q30-student-wants-determine-focal-length

ScienceCBSE Class 10 · Sample paper, session 2026-27 · 1 mark · MCQ

CBSE Class 10 Science sample paper 2026-27: question 30

From the official CBSE sample question paper for 2026-27, section C, question 30, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q30 · 1 mark · MCQCompetency-basedLight – Reflection and Refraction

A student wants to determine the focal length of a convex lens using sunlight. Which of the following practical procedures will give the most accurate result?

  1. (A)Move the lens close to a wall and measure the blurred circle.
  2. (B)Hold the lens above a sheet of paper and adjust until the smallest, brightest spot is formed.
  3. (C)Measure the thickness of the lens with a scale.
  4. (D)Look through the lens at a distant object.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

Where do parallel rays meet after passing through a convex lens?

Hint 2

How would you locate that point exactly on a sheet of paper?

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. Sunlight comes from a very distant object, so its parallel rays converge at the principal focus of the convex lens.

    ½ mark

  2. The smallest, brightest spot on the paper marks the focus. The lens-to-paper distance is then the focal length. Answer: (B).

    ½ mark

Answer: Option (B)

Where the marks are

  • Explains that the sharpest, smallest spot lies at the focus; chooses (B) (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Light – Reflection and Refraction, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: 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.