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The above image shows… (Class 10 Science SQP 2025-26, Q33)

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ScienceCBSE Class 10 · Sample paper, session 2025-26 · 2 marks · Case-based

CBSE Class 10 Science sample paper 2025-26: question 33

From the official CBSE sample question paper for 2025-26, section C, question 33, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q33 · 2 marks · Case-basedCompetency-basedLight – Reflection and Refraction

The above image shows the formation of an image with an optical instrument.

  1. A

    Identify the optical instrument (shown schematically as a rectangle) in the image.

    1 mark
  2. B

    What type of image is formed in this case?

    1 mark
  3. C

    Based on the measurements given in the image, calculate the focal length of the instrument.

    1 mark

Figure in the paper: A horizontal principal axis with a vertical rectangle (the optical element) in the middle. An upright object arrow stands on the left of the rectangle; a smaller upright arrow appears on the same left side, with rays drawn from the top of the object through the element and emerging diverging to the right, and dotted lines extended backwards to meet at the image top. Measurements: 10 cm marked from the rectangle to the foot of the smaller arrow, and 20 cm marked from the object foot to the rectangle. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

Do the emerging rays meet, or only their backward extensions?

Hint 2

Both object and image are on the left of the lens, so both u and v are negative.

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 rays diverge after passing through the element, and the diminished, erect image is on the same side as the object. So the instrument is a concave (diverging) lens.

    ½ mark

  2. B. The image is virtual, erect and diminished. It is formed where the backward extensions of the rays meet.

    ½ mark

  3. C. Lens formula with cm and cm (image on the object side).

  4. cm

    1 mark

  5. For visually impaired students: A. A convex lens forms a virtual image when the object is placed between its optical centre and principal focus F. B. A convex lens converges the parallel rays of sunlight to its focus. The light energy concentrated at that small spot raises the temperature enough to ignite the paper.

Answer: A. Concave lens; B. Virtual (erect, diminished); C. f = −20 cm

Where the marks are

  • Identifies concave lens (½ mark)
  • Virtual image (½ mark)
  • Correct substitution with signs and f = −20 cm (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 2025-26: 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.