Waves & The Electromagnetic Spectrum

Band-by-band uses

Why each band suits its job

• Radio waves are absorbed only weakly by air and the ground, and pass through walls; that makes them ideal for long-range broadcasting
• Microwaves of certain frequencies are absorbed strongly by water molecules in food, transferring energy quickly to the water and heating the meal. Other microwave frequencies pass through the atmosphere and most weather, so they are used by mobile-phone and satellite networks
• Infrared is given off by anything warm (including human bodies), so cameras tuned to IR can see in the dark; the same waves can be aimed at heating elements where the goal is to deliver warmth quickly
• Visible light can be focused with simple lenses and detected by the eye and by silicon sensors, which is the basis of vision, photography and fibre-optic data
• Ultraviolet carries enough energy per photon to break some chemical bonds, which is why it can sterilise surfaces and make fluorescent inks glow in security applications
• X-rays are absorbed by dense materials such as bone but pass through soft tissue, producing a "shadow" image
• Gamma rays are the most energetic band, easily killing living cells, which is exactly what is wanted when sterilising equipment or targeting tumour cells in radiotherapy