# Electromagnetic spectrum

A family of transverse waves that all travel at the speed of light in a vacuum (300,000,000 m/s). From long to short wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.

Physics (school) · Part 05: Waves, sound and light · Card 6 of 8 · Last updated 2026-10-19

## Analogy

Like a piano keyboard: different notes (frequencies) but all the same instrument (electromagnetic waves).

## Example

**Order of waves**

Radio, Microwave, Infrared,
Visible, Ultraviolet, X-ray, Gamma
long wavelength to short
low energy to high energy

## In practice

Radio carries TV signals, microwaves heat food, X-rays show bones and gamma rays treat cancer.

## Practice

### Flashcards

- **Name the electromagnetic waves from longest to shortest wavelength.** Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.

### Interview questions

**Describe two differences between sound waves and light waves.**

- Sound is longitudinal and light is transverse
- Sound needs a material but light can cross a vacuum
- Light is much faster than sound

## Questions people ask

### Which electromagnetic waves are dangerous?

Ultraviolet, X-rays and gamma rays carry enough energy to damage living cells, which can cause sunburn, skin cancer or other harm. Higher-frequency waves carry more energy. This is why you wear sunscreen, and why radiographers stand behind screens when taking X-rays.

### How fast do electromagnetic waves travel?

All electromagnetic waves travel at about 300,000,000 m/s in a vacuum, the speed of light. They only differ in frequency and wavelength. Light from the Sun takes around eight minutes to reach Earth because it has to cross about 150 million kilometres of space.

## Related concepts

- [Waves](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-1)
- [Sound](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-7)
- [Reflection](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-4)
- [Refraction](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-5)

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