Radio and microwave wavelengths are long (cm to km). Low-energy electromagnetic radiation that carries broadcast signals, Wi-Fi, GPS.
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y = sin(k · x)
Frequency–wavelength for light
Radio waves are just low-frequency electromagnetic waves. FM radio near 100 MHz has λ ≈ 3 m; a 2.4 GHz Wi-Fi wave has λ ≈ 12.5 cm.
Across the radio band
- Long wave / AM — kilometres long, bends over hills, travels far.
- FM / TV — metres, line-of-sight-ish.
- Microwaves — centimetres: Wi-Fi, GPS, radar, phone signals.
- All travel at the speed of light and need no medium — they cross empty space.
Your phone, the Sun, and a hot cup of tea all emit electromagnetic waves — radio is simply the longest, lowest-energy end of the same spectrum as visible light.