Electromagnetic Radiation

EM spectrum, properties and applications

The Electromagnetic Spectrum

Electromagnetic (EM) radiation is a form of energy that travels as transverse waves at the speed of light (3 × 10⁸ m·s⁻¹). The EM spectrum, from longest to shortest wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Properties of EM Radiation

All EM waves: • Travel at the speed of light in a vacuum • Do not need a medium (can travel through space) • Are transverse waves • Carry energy The relationship: c = fλ, where c = 3 × 10⁸ m·s⁻¹. Higher frequency = shorter wavelength = more energy.

Example

Applications

• Radio waves — broadcasting (e.g. SABC radio stations) • Microwaves — cooking food, cell phone signals • Infrared — remote controls, thermal imaging • Visible light — sight, fibre optics • Ultraviolet — sterilisation, sun causes tanning/burning • X-rays — medical imaging • Gamma rays — cancer treatment, sterilising medical equipment

Note

Dangers and Protection

UV radiation from the sun is particularly strong in South Africa. Prolonged exposure causes skin cancer and eye damage. Wear sunscreen (SPF 30+), sunglasses and a hat. X-rays and gamma rays are ionising — they can damage cells and DNA.

Key Vocabulary

Electromagnetic spectrumThe range of all types of electromagnetic radiation

WavelengthThe distance between two consecutive crests of a wave

FrequencyThe number of wave cycles per second (Hz)

Speed of light3 × 10⁸ m·s⁻¹ — the speed EM waves travel in a vacuum

Ionising radiationHigh-energy radiation that can remove electrons from atoms

SASL Avatar

Loading avatar...

1 / 5

Electromagnetic spectrum

Speed: