Electromagnetic Waves: Uses

Electromagnetic (EM) waves carry energy and do not need a medium. In a vacuum, they all travel at the same speed, about $3.0 \times 10^8\,\text{m s}^{-1}$. Different regions have different wavelengths and energies, so we use them for different jobs.

Order of the spectrum

From lowest frequency (longest wavelength) to highest: radio → microwaves → infrared (IR) → visible → ultraviolet (UV) → X-rays → gamma rays.

Typical uses by region

Radio waves

• Broadcasting: radio and television transmissions over large areas.
• Astronomy: radio telescopes study distant stars and galaxies.
• RFID: tags in shop goods and travel cards for quick identification.

Microwaves

• Communication: mobile phones and satellite television links.
• Cooking: microwave ovens heat food by making water molecules vibrate faster.

Infrared (IR)

• Heating: electric grills and heaters emit IR you feel as warmth.
• Controls and sensors: TV remote controllers; intruder alarms detect body heat.
• Imaging and data: thermal cameras show heat patterns; optical fibres carry IR light through glass.

Visible light

• Vision: enables seeing.
• Photography: cameras record visible images.
• Illumination: lamps and LEDs light spaces.

Ultraviolet (UV)

• Security marking: special inks glow under UV.
• Detecting fake notes: banknotes have UV features.
• Sterilising water: UV kills microorganisms.

X-rays

• Medical scanning: images of bones and teeth.
• Security scanners: check luggage contents.

Gamma rays

• Sterilisation: kill bacteria on food and medical equipment.
• Cancer care: detect and treat cancers (radiotherapy).

Why these uses fit

• Longer wavelengths (radio) spread around hills and buildings, good for broadcasting.
• Microwaves pass through clouds and some walls, reaching satellites and phones; they heat water-rich food efficiently.
• IR is emitted by warm objects and is felt as heat, so it suits heaters and thermal cameras.
• UV, X-rays, and gamma rays have higher energy, so they can cause fluorescence (security inks), kill germs (UV), and penetrate tissues (X and gamma for imaging and treatment).

Safety snapshot (excessive exposure)

• Microwaves: internal heating of body cells.
• Infrared: skin burns.
• Ultraviolet: skin and eye damage; can lead to skin cancer.
• X-rays and gamma rays: can damage or mutate cells.