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When and where does a… (Class 10 Science 2023, Q24a)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 24(a)

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, section B, question 24(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q24(a) · 2 marks · Very short answerThe Human Eye and the Colourful World

When and where does a rainbow appear in the sky ? Draw a labelled ray diagram to show its formation.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/2/1.

Hints

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

Hint 1

Water droplets must be present in the air. When does that happen?

Hint 2

Where is the Sun relative to you when you see a rainbow?

Hint 3

Inside a raindrop, light refracts, reflects once internally and refracts again.

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. When: A rainbow appears just after a rain shower, when tiny water droplets are still suspended in the air and the Sun is shining.

    ½ mark

  2. Where: It always appears in the part of the sky opposite to the Sun, so the observer must stand with the Sun behind them.

    ½ mark

  3. Labelled ray diagram (described):

    • Draw a spherical raindrop with a ray of white sunlight entering it.
    • The light refracts and disperses at the first surface.
    • It undergoes internal reflection at the back of the drop.
    • It refracts again as it leaves the drop, spreading into a spectrum.
    • Label the incoming ray 'Sunlight', and label the emerging rays 'Red' and 'Violet'.
    • Mark the steps 'Refraction and dispersion', 'Internal reflection' and 'Refraction'.
    • Show arrows on all rays.
    1 mark

Answer: After a rain shower, in the direction opposite to the Sun; formed by refraction and dispersion, internal reflection and refraction in raindrops.

Where the marks are

  • When: after a rain shower (½ mark)
  • Where: opposite to the Sun (½ mark)
  • Correct ray diagram through a raindrop showing refraction, dispersion, internal reflection and labelled red and violet rays (1 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 paper2023 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.