Uses of Electromagnetic Waves (Cambridge International IGCSE Physics)

Spec point — 3.3.2 · Describe typical uses of the different regions of the electromagnetic spectrum including: (a) radio waves; radio and television transmissions, astronomy, radio frequency identification (RFID) (b) microwaves; satellite television, mobile phones (cell phones), microwave ovens (c) infrared; electric grills, short range communications such as remote controllers for televisions, intruder alarms, thermal imaging, optical fibres (d) visible light; vision, photography, illumination (e) ultraviolet; security marking, detecting fake bank notes, sterilising water (f) X-rays; medical scanning, security scanners (g) gamma rays; sterilising food and medical equipment, detection of cancer and its treatment

Uses of electromagnetic waves

Uses of radio and microwaves

• The main uses of radio and microwaves are for wireless communication

  • Many things people often assume use radio waves actually use microwaves (e.g., Wi-Fi, radar, mobile phones, satellite communications)

• At very high intensities, microwaves can also be used to heat food

  • This is what happens in a microwave oven

Uses of infrared

• Warm objects emit infrared radiation

• Infrared can be detected using thermal imaging cameras:

  • in security cameras, for research, and also in medicine

• Remote controls have small infrared LEDs that 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

  • So most fibre optic communication systems use infrared

Uses of visible light

• Visible light is the only part of the electromagnetic spectrum that the human eye can see
• Visible light is used for photography, videography, and illumination

Uses of ultraviolet light

• Ultraviolet is responsible for giving the skin a suntan, which is the body’s way of protecting itself against ultraviolet rays

• When certain substances are exposed to ultraviolet light, they absorb 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
  • Most bank notes have invisible fluorescent markings on them

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

Uses of X-rays

• The most obvious use of X-rays is in medicine

• X-rays pass through body tissues but are absorbed by denser body parts, such as bones

  • Bones absorb X-rays, leaving a shadow that can be seen using photographic film

Uses of gamma rays

• Gamma rays are used to kill cells and living tissue

• This property is utilised in both cancer detection and treatment

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

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

Typical uses of the different regions of the electromagnetic spectrum

Summary of the uses and dangers of the electromagnetic spectrum

Uses and dangers of the electromagnetic spectrum