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Long Red Waves, Short Blue Waves
Age 15 · Physics
Light is an electromagnetic wave, and every colour has its own wavelength. Red light spreads over a longer wavelength, while blue and violet pack into a shorter one.
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Age 15: open this week
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In the picture
- The gap between two red crests: one long wavelength
- The gap between two blue-violet crests: one short wavelength
- A crest of the red wave: the high point of a long, stretched cycle
- A crest of the blue-violet wave: a high point in a tightly packed cycle
Examples
- Sunlight spread by a prism into a rainbow, red at one end and violet at the other
- A red tail light and a blue LED glowing side by side
Key takeaways
- Wavelength sets the colour: long waves look red, short waves look blue or violet
- In a vacuum all colours travel at the same speed, so shorter wavelengths complete more cycles each second
Quiz: Long Red Waves, Short Blue Waves (Age 15)
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According to the card, which colour has the longest wavelength?
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What sets the colour of light?
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In a vacuum, what is true about light of different colours?
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