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The above figure shows… (Class 10 Science SQP 2024-25, Q24)

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ScienceCBSE Class 10 · Sample paper, session 2024-25 · 2 marks · Very short answer

CBSE Class 10 Science sample paper 2024-25: question 24

From the official CBSE sample question paper for 2024-25, section B, question 24, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q24 · 2 marks · Very short answerLight – Reflection and Refraction

The above figure shows the formation of an image by a lens shown by a thick line.
Analyse the figure and answer the following questions.
A. What is the type of lens used?
B. What is the nature of the image?
C. If the image is formed at a distance of 30 cm from the lens and the image is twice the size of the object, then where is the object placed?

(For visually impaired students: A. What type of lens always forms a virtual erect and diminished image? B. List two uses of such a lens.)

Figure in the paper: A thick vertical line represents a lens with a horizontal principal axis. A small upright object arrow is on the left of the lens; a ray parallel to the axis from its tip hits the lens and bends downward-away (diverges), and another ray passes undeviated through the optical centre. Dotted backward extensions meet on the left forming a larger upright image arrow farther from the lens than the object. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

An enlarged, upright image on the same side as the object is formed by only one type of lens. Which one?

Hint 2

Is the image formed by actual rays or by their backward extensions?

Hint 3

Use , taking as negative for a virtual image.

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 image is upright, larger than the object and on the same side as the object. Only a converging lens forms such an image, with the object between and . So the lens is a convex lens.

    ½ mark

  2. B. The image is formed where the backward (dotted) extensions of the refracted rays meet, on the same side as the object. It is therefore virtual (and also erect and enlarged).

    ½ mark

  3. C. For a lens, . The image is virtual and erect, so and cm (same side as the object).

    ½ mark

  4. cm. The object is placed 15 cm in front of the lens, on the same side as the image.

    ½ mark

  5. (For visually impaired students) A. A concave lens always forms a virtual, erect and diminished image. B. Two uses: correcting myopia (short-sightedness) and door peepholes (also some torches and spectacles).

Answer: A. Convex lens; B. Virtual (erect, enlarged); C. u = −15 cm, i.e. 15 cm in front of the lens. (VI: concave lens; used to correct myopia and in door peepholes)

Where the marks are

  • Identifies the lens as convex (0.5 mark)
  • States that the image is virtual (0.5 mark)
  • Uses with cm (0.5 mark)
  • Obtains cm (0.5 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 2024-25: 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.