Physics › Section R · Electromagnetic waves and geometric optics › Topic R.5
Dispersion: rainbows and prisms
Sunlight looks white, yet a glass prism or a curtain of raindrops spreads it into a band of colours. The reason is that a material's index of refraction depends slightly on the wavelength of the light, so each colour bends by its own angle.
In this topic
- White light is a mixture
- Why the colours bend differently
- How big is the effect?
- Worked example: colours entering glass
- Prisms bend the light twice
- Worked example: through a 60° prism
- Rainbows: refraction, reflection, refraction
- Worked example: the 42° angle
- Why a bow, and which way round
- Dispersion at work, and as a nuisance
- Common mistakes to avoid
- Key takeaways
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