Uses of Electromagnetic Waves (Cambridge O Level Physics)

• Electromagnetic waves have a variety of uses and applications

Table of Applications of EM Waves

Wave	Use
Radio	Communication (radio and TV) Astronomy
Microwave	Heating food (microwave ovens) Communication (WiFi, mobile phones, Bluetooth, satellite TV, satellites)
Infrared	Remote controls Fibre optic communications Thermal imaging (medicine and industry) Night vision Heating and cooking Motion sensors (for security alarms) Electrical heaters Infrared cameras
Visible light	Vision Photographs/videos
Ultraviolet	Security markings (fluorescence) Detecting counterfeit bank notes Sterilising water
X-rays	Medical (and dental) imaging Security scanners (at airports etc.) Killing cancerous cells Engineering applications (detecting cracks in metals)
Gamma rays	Sterilising food Sterilising medical equipment Detecting & treating cancerous cells Engineering applications (detecting cracks in metals)

A summary of the Uses and Dangers of EM Waves 

Uses and dangers of the electromagnetic spectrum

Radio Waves & Microwaves

• These two parts of the spectrum share a lot of similarities and applications
  • Their main uses concern wireless communication – in fact, many things that people often assume use radio waves actually use microwaves (e.g. WiFi, radar, mobile phones, satellite communications)

• At very high intensities microwaves can also be used to heat things
  • This is what happens in a microwave oven

Infrared

• Infrared is emitted by warm objects and can be detected using special cameras (thermal imaging cameras). These can be used in industry, in research and also in medicine
• Many security cameras are capable of seeing slightly into the infrared part of the spectrum and this can be used to allow them to see in the dark
  • Infrared lights are used to illuminate an area without being seen, which is then detected using the camera
• Remote controls also have small infrared LEDs that can send invisible signals to an infrared receiver on a device such as a TV
• Infrared travels down fibre optic cables more efficiently than visible light, and so most fibre optic communication systems use infrared

Visible

• Visible light is the only part of the electromagnetic spectrum that the human eye can see
• The human eye can detect wavelengths from 750 nanometres (red light) up to 380 nanometres (violet light)

Ultraviolet

• Ultraviolet is responsible for giving you a sun tan, which is your body’s way of protecting itself against the ultraviolet
• When certain substances are exposed to ultraviolet, they absorb it and re-emit it as visible light (making them glow)
  • This process is known as fluorescence
  • Fluorescence can be used to secretly mark things using special ink – in fact, most bank notes have invisible fluorescent markings on them

• Fluorescent light bulbs also use this principle to emit visible light

X-rays

• The most obvious use of x-rays is in medicine
• X-rays are able to pass through most body tissues but are absorbed by the denser parts of the body, such as bones
  • When exposed to x-rays, the bones absorb the x-rays, leaving a shadow which can be seen using a special x-ray detector or photographic film

Gamma Rays