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An object is placed at a… (Class 10 Science 2025, Q12)

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ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 12

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section A, question 12, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q12 · 1 mark · MCQLight – Reflection and Refraction

An object is placed at a distance of 30 cm from the pole of a concave mirror. If its real and inverted image is formed at 60 cm in front of the mirror, the focal length of the mirror is :

  1. (A) cm
  2. (B) cm
  3. (C) cm
  4. (D) cm

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

Distances in front of the mirror are negative.

Hint 2

Use .

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. By the sign convention, the object and the real image are both in front of the mirror: cm, cm.

  2. Mirror formula:

  3. cm: (B).

    1 mark

Answer: cm, option (B)

Where the marks are

  • Applies the mirror formula with correct signs to get cm, option (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 paper2025 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.