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Draw a ray diagram to show… (Class 10 Science 2024, Q31b)

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ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 3 marks · Diagram

CBSE Class 10 Science 2024: question 31(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, section C, question 31(b), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q31(b) · 3 marks · DiagramThe Human Eye and the Colourful World

Draw a ray diagram to show the formation of a rainbow in the sky. On this diagram mark A – where dispersion of light occurs, B – where internal reflection of light occurs and C – where refraction of light occurs. List two necessary conditions to observe a rainbow.

Figure in the paper: Ray diagram to be drawn showing sunlight entering a water droplet, dispersion, internal reflection and refraction on exit, with points A (dispersion), B (internal reflection) and C (refraction) marked. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/2/1.

Hints

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

Hint 1

Each raindrop acts like a tiny prism; light enters, reflects once at the back, then leaves.

Hint 2

Think about when and in which direction you look to see a rainbow.

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. Ray diagram (described): Draw a circle for a raindrop. A ray of sunlight strikes the drop on the upper left at point A, refracts into the drop and splits into colours. These rays travel to the back of the drop at B, reflect inside, and travel to C on the lower left, where they refract out towards the observer as separate coloured rays.

    ½ mark

  2. Marking: A, entry point where refraction and dispersion of white light occur; B, back surface where internal reflection occurs; C, exit point where refraction occurs as light leaves the drop.

    1½ marks

  3. Condition 1: Tiny water droplets must be present in the atmosphere (just after a shower).

    ½ mark

  4. Condition 2: The Sun must be behind the observer, with the observer facing the droplets.

    ½ mark

Answer: Diagram: raindrop with dispersion at A, internal reflection at B, refraction at C. Conditions: water droplets in the air; Sun behind the observer.

Where the marks are

  • Correct ray diagram through a raindrop (½ mark)
  • Correct marking of A, B and C (½ × 3 marks)
  • Water droplets present in the atmosphere (½ mark)
  • Sun behind the observer (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from The Human Eye and the Colourful World, one at a time, marked against the answer key and marking points.Back to the full paper2024 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.