Uses of Electromagnetic Waves (Cambridge (CIE) O Level Physics): Revision Note

Uses of Electromagnetic Waves

• Electromagnetic waves have a variety of uses and applications

Table of Applications of EM Waves

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

• Gamma rays are very dangerous and can be used to kill cells and living tissue

• This property can be utilised in both cancer detection and treatment 

  • If these gamma rays are carefully aimed at cancerous tissue, they can be very effective at destroying the cancerous cells

• Gamma rays can also be used to sterilise food and medical equipment by killing off the bacteria