2 marksShort AnswerSection A

What is meant by the dispersion of white light? Draw a diagram to show dispersion of white light by the glass prism.

Q: What is meant by the dispersion of white light? Draw a diagram to show dispersion of white light by the glass prism.

**Dispersion of White Light:** The splitting of a beam of white light into its seven constituent colours (Violet, Indigo, Blue, Green, Yellow, Orange, and Red) when it passes through a refracting medium like a glass prism is called **dispersion**. **Reason for Dispersion:** Different colours of light bend through different angles with respect to the incident ray as they pass through a prism. Red light bends the least, while violet light bends the most. This causes the different colours to emerge along distinct paths, forming a spectrum. **Diagram of Dispersion through a Glass Prism:** ```diagram {"xrange": [8.0, 442.0], "yrange": [-240.4, -29.6], "lines": [{"from": [150, -220], "to": [250, -50], "label": "Glass Prism"}, {"from": [250, -50], "to": [350, -220], "label": ""}, {"from": [50, -160], "to": [200, -135], "label": "White Light Beam"}, {"from": [200, -135], "to": [280, -115], "label": ""}, {"from": [200, -135], "to": [290, -155], "label": ""}, {"from": [280, -115], "to": [400, -90], "label": "Red (bends least)"}, {"from": [290, -155], "to": [400, -180], "label": "Violet (bends most)"}]} ```

The Human Eye and the Colourful World

Refraction of Light through a Prism

Official Answer

Dispersion of White Light:

The splitting of a beam of white light into its seven constituent colours (Violet, Indigo, Blue, Green, Yellow, Orange, and Red) when it passes through a refracting medium like a glass prism is called dispersion.

Reason for Dispersion:

Different colours of light bend through different angles with respect to the incident ray as they pass through a prism. Red light bends the least, while violet light bends the most. This causes the different colours to emerge along distinct paths, forming a spectrum.

Diagram of Dispersion through a Glass Prism:

splitting of lightcomponent coloursdispersionglass prismbends the leastbends the mostspectrum

Marking Scheme

1Definition of dispersion of white light (1 mark)
2Neat, labeled ray diagram showing white light splitting into red and violet components through a glass prism (1 mark)

Hint

Remember the acronym VIBGYOR and think about which colour bends the most and which bends the least when passing through glass.

Quick Oral Answer

Dispersion is the splitting of white light into its seven constituent colours when it passes through a prism. Red bends the least because it has the longest wavelength, and violet bends the most.

Analysis & Explanation

White light is a mixture of seven colours. When it enters a glass prism, the refractive index of glass is slightly different for each colour (wavelength) of light. Because of this, each colour travels at a different speed inside the prism and bends by a different angle. Red light travels fastest and bends the least, whereas violet light travels slowest and bends the most, splitting the white light into a beautiful band of colours called a spectrum.

Common Mistakes

1Drawing the emergent rays parallel to each other (which happens in a glass slab, not a prism).
2Reversing the order of colours (e.g., drawing violet at the top and red at the bottom).

Interesting Facts

Sir Isaac Newton was the first scientist to use a glass prism to obtain the spectrum of sunlight, proving that sunlight is actually made up of seven distinct colours.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2011?

This question carries 2 marks in the CBSE Class 10 Science 2011 examination.

Which chapter does this question come from in Science?

This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Refraction of Light through a Prism" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2011 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.