Dispersion of light
Cambridge IGCSE Physics (0625) · Unit 3: Waves · 6 flashcards
Dispersion of light is topic 3.2.4 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 3 — Waves , alongside General properties of waves, Reflection of light and Refraction of light. In one line: Monochromatic light is visible light consisting of a single frequency or wavelength. This means it appears as a single color and cannot be further dispersed into other colors by a prism or diffraction grating. It has a single, well-defined index of refraction for a given material.
This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).
The deck below contains 6 flashcards — 1 definition — covering the precise wording mark schemes reward. Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
The term 'monochromatic light'
Monochromatic light is visible light consisting of a single frequency or wavelength. This means it appears as a single color and cannot be further dispersed into other colors by a prism or diffraction grating. It has a single, well-defined index of refraction for a given material.
What the Cambridge 0625 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Describe Describe the dispersion of light as illustrated by the refraction of white light by a glass prism
- Know Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength
- Recall Recall that visible light of a single frequency is described as monochromatic Supplement
Describe what happens to white light as it passes through a glass prism, explaining why this phenomenon occurs. Include a diagram to illustrate your answer.
When white light enters a glass prism, it refracts. Different colors of light within white light have different wavelengths. Shorter wavelengths (like violet) refract more than longer wavelengths (like red). This causes the white light to separate into its constituent colors, forming a spectrum. This separation is called dispersion. The diagram should show white light entering the prism, separating into different colours (red, orange, yellow, green, blue, indigo, violet), and each colour refracting at a slightly different angle.
State the term used to describe the separation of white light into its constituent colours when it passes through a prism. Briefly explain why different colours separate.
The term is dispersion. Different colours of light have different wavelengths. When white light enters the prism, each wavelength refracts by a slightly different amount. Shorter wavelengths, like violet, bend more than longer wavelengths, like red, causing the colours to separate.
State the seven traditional colours of the visible spectrum in order of increasing wavelength, starting with the colour that has the shortest wavelength.
1. Violet
2. Indigo
3. Blue
4. Green
5. Yellow
6. Orange
7. Red
These colours are ordered from shortest wavelength (highest frequency) to longest wavelength (lowest frequency). Remembering 'VIBGYOR' can help you recall the order.
Describe how the frequency of light changes as you move through the visible spectrum from red to violet.
As you move from red to violet in the visible spectrum, the frequency of light increases. Red has the lowest frequency, while violet has the highest frequency of the colours in the visible spectrum. This corresponds to a decrease in wavelength.
Define the term 'monochromatic light'.
Monochromatic light is visible light consisting of a single frequency or wavelength. This means it appears as a single color and cannot be further dispersed into other colors by a prism or diffraction grating. It has a single, well-defined index of refraction for a given material.
State a common example of a source of monochromatic light.
A laser emitting a specific color (
Key Questions: Dispersion of light
Define the term 'monochromatic light'.
Monochromatic light is visible light consisting of a single frequency or wavelength. This means it appears as a single color and cannot be further dispersed into other colors by a prism or diffraction grating. It has a single, well-defined index of refraction for a given material.
More topics in Unit 3 — Waves
Dispersion of light sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Dispersion of light deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
Related Physics guides
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