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The above ray diagram is to… (Class 10 Science 2026, Q38)

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ScienceCBSE Class 10 · Board exam 2026, set 31/4/1 · 4 marks · Case-based

CBSE Class 10 Science 2026: question 38

Set in the CBSE Class 10 board exam of 2026, paper 31/4/1, section C, question 38, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q38 · 4 marks · Case-basedCompetency-basedLight – Reflection and Refraction

The above ray diagram is to show image formation by a reflecting telescope. Reflecting telescope revolutionized our way of looking into the sky. Reflecting telescopes employ large mirrors to gather and focus light rather than relying solely on lenses as we do in the refracting telescopes. These telescopes utilize precisely shaped and polished mirrors to capture incoming light and reflect it to a focal point, where the telescope forms an image for observation.

  1. (a)

    What kind of image of a star is seen by the observer in the eye-piece?

    0 marks
  2. (b)

    What kind of mirror is used in this reflecting telescope?

    0 marks
  3. (c)

    Explain with the reason, what kind of optical device (type of lens or mirror) is used at the eye-piece.

    0 marks

  4. OR

    (c)

    OR: What is the role of plane mirror in image formation by this telescope?

    0 marks

Figure in the paper: Ray diagram of a reflecting telescope. Parallel light rays from a distant star enter from the left and strike a large curved (concave) mirror on the right. The reflected rays converge towards a small plane mirror placed at an angle in the tube, which deflects them downwards out of the side of the tube to an eye-piece (a convex lens) at the bottom, where the rays emerge converging towards the observer. Labels: 'Parallel Light Rays from distant star', 'Curved Mirror', 'Plane Mirror', 'Eye-piece'. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/4/1.

Hints

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

Hint 1

Parallel rays from a star meeting at a point: which type of mirror does that?

Hint 2

An eye-piece works like a magnifying glass. Which lens is a magnifying glass?

Hint 3

Look at where the eye-piece sits relative to the main mirror: how do the rays get there?

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 concave mirror forms a real image of the star near its focus. The eye-piece magnifies it, so the observer sees a magnified image of the star.

    1 mark

  2. (b) The main mirror is a concave (converging) mirror. A plane mirror is also used to deflect the rays.

    1 mark

  3. (c) A convex lens is used at the eye-piece.

    1 mark

  4. Reason: the real image formed by the concave mirror lies within the focal length of the convex eye-piece, which then acts as a magnifier. It produces an enlarged image that the eye can view clearly.

    1 mark

  5. (c) OR: The plane mirror intercepts the converging rays reflected by the concave mirror. It reflects (redirects) them sideways out of the tube towards the eye-piece, so the observer can view the image without blocking the incoming starlight.

    2 marks

Answer: (a) Real, magnified image; (b) concave (converging) mirror, along with a plane mirror; (c) convex lens, as it magnifies the image formed by the curved mirror. OR (c) The plane mirror redirects the reflected rays towards the eye-piece.

Where the marks are

  • Image real/magnified (1 mark)
  • Concave (converging) mirror, plane mirror (1 mark)
  • Convex lens at eye-piece (1 mark)
  • Reason: magnifies image formed by curved mirror (1 mark)
  • OR: plane mirror reflects/redirects rays from curved mirror to eye-piece (2 marks)

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 paper2026 board paper, set 31/4/1: 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.