Each region of the electromagnetic spectrum has properties that make it suitable for specific applications.
Uses by region
| Region | Uses | Why this region works |
|---|---|---|
| Radio waves | Television, radio broadcasting, communication | Long wavelength travels long distances and diffracts around buildings and hills |
| Microwaves | Mobile phone signals, satellite communication, microwave ovens | Specific frequencies absorbed by water molecules (cooking); can pass through the atmosphere (satellite links) |
| Infrared | Remote controls, thermal imaging, optical fibre communication, heaters | Emitted by warm objects; detected by sensors; travels through glass fibres |
| Visible light | Seeing, photography, optical fibre communication | Detected by the human eye; carries information through optical fibres |
| Ultraviolet | Fluorescent lighting, security marking, sterilisation | Causes certain materials to fluoresce; kills bacteria |
| X-rays | Medical imaging (bones, teeth), airport security scanners | Passes through soft tissue but absorbed by bone and metal |
| Gamma rays | Sterilising medical equipment, treating cancer (radiotherapy), detecting leaks in pipes | Very penetrating; kills cells (useful and dangerous) |
Linking properties to uses
When explaining why a particular wave is used:
- Name the property (e.g. “passes through soft tissue”).
- Explain how this property makes it useful for the application (e.g. “so bone fractures can be seen on an X-ray image”).
Worked example
Explain why microwaves are used for satellite communication.
Microwaves can pass through the Earth’s atmosphere without being significantly absorbed. They can be directed in narrow beams toward a satellite and received at a dish antenna on the ground. Radio waves would spread too much, and higher-frequency waves (UV, X-ray) would be absorbed or scattered.
Common errors and how to correct them
Mixing up infrared and ultraviolet uses. Infrared is associated with heat and remote controls. Ultraviolet causes fluorescence and kills bacteria. Do not swap them.
Saying “gamma rays are used for X-rays.” X-rays and gamma rays are different parts of the spectrum. Medical imaging uses X-rays; cancer treatment and sterilisation typically use gamma rays.
How to apply this in an exam
State the specific wave region, name the application, and explain why that type of wave is suited to the application (link the property to the use). One clear example per region is sufficient.
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