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What is dispersion of white… (Class 10 Science 2024, Q31b)

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ScienceCBSE Class 10 · Board exam 2024, set 31/5/1 · 3 marks · Short answer

CBSE Class 10 Science 2024: question 31(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/5/1, 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 · Short answerThe Human Eye and the Colourful World

What is dispersion of white light? State its cause. Draw a diagram to show dispersion of a beam of white light by a glass prism.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/5/1.

Hints

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

Hint 1

Think of what you see on a screen when sunlight passes through a prism.

Hint 2

Each colour has its own amount of bending in glass. Which colour bends least and which bends most? That decides the order in your diagram.

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. Dispersion: the splitting of white light into its seven constituent colours (VIBGYOR) on passing through a transparent medium such as a glass prism.

    1 mark

  2. Cause: the different colours of white light bend through different angles with respect to the incident ray. Red bends the least and violet bends the most, so the colours separate.

    1 mark

  3. Diagram (described): draw a triangular glass prism. A narrow beam of white light falls obliquely on one refracting face. Inside the prism the beam spreads out, and it emerges from the second face as a band of colours on a screen. Label the colours from top to bottom as Red, Orange, Yellow, Green, Blue, Indigo, Violet (violet deviated most, at the bottom; red at the top). Show arrows on all rays and label 'white light' and 'spectrum'.

    1 mark

Answer: Dispersion is the splitting of white light into its seven colours. It occurs because different colours bend through different angles (red least, violet most). Diagram: prism forming a VIBGYOR spectrum with red at the top and violet at the bottom.

Where the marks are

  • Defines dispersion as splitting of white light into its constituent colours (1 mark)
  • States that different colours bend through different angles (1 mark)
  • Draws the prism diagram with the spectrum correctly ordered and labelled, with arrows (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 paper2024 board paper, set 31/5/1: 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.