Electromagnetic Spectrum
Region
Radio
Frequency
30 MHz
Wavelength
10 m
Energy (eV)
1.2Γ—10⁻⁷
Example use
FM radio
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All EM Waves

All EM waves travel at c = 2.998 Γ— 10⁸ m/s in a vacuum. They are transverse waves with oscillating electric and magnetic fields, requiring no medium. All obey c = f Γ— Ξ».

c = f Γ— Ξ»  =  3 Γ— 10⁸ m/s

Radio Waves

Wavelengths from about 1 mm to thousands of km; frequencies below ~300 GHz. Used in AM/FM radio, television, WiFi, Bluetooth, mobile phones, and MRI scanners. Produced by oscillating charges in aerials.

Microwaves

Wavelengths 1 mm – 1 m; frequencies 300 MHz – 300 GHz. Used in microwave ovens (2.45 GHz resonates water molecules), radar, satellite communication, and some mobile networks.

Infrared (IR)

Wavelengths 700 nm – 1 mm; frequencies ~300 GHz – 430 THz. All objects above absolute zero emit IR. Used in thermal cameras, remote controls, optical fibre comms, and night-vision equipment.

Visible Light

Wavelengths 380–700 nm; frequencies 430–790 THz. The only region detected by the human eye. Violet is shortest wavelength; red is longest. White light contains all visible wavelengths.

Ultraviolet (UV)

Wavelengths 10–380 nm; frequencies 790 THz – 30 PHz. Produced by the Sun and UV lamps. Causes sunburn and skin cancer by damaging DNA. Also used for sterilisation, fluorescence, and security marking.

X-rays

Wavelengths 0.01–10 nm; frequencies 30 PHz – 30 EHz. Penetrate soft tissue but are absorbed by dense bone, making them useful for medical imaging. Ionising radiation β€” can cause cell damage and cancer.

Gamma Rays

Wavelengths below 0.01 nm; frequencies above 30 EHz. Emitted from atomic nuclei during radioactive decay. Highly ionising and penetrating. Used in cancer radiotherapy (Ξ³-knife) and sterilisation of medical equipment.