Formula
| c = λ · f | speed of wave = wavelength × frequency |
|---|---|
| λ (EM waves) | = c / f = 299 792 458 / f (m) |
| λ (sound) | = v_sound / f ≈ 343 / f (m at 20 °C in air) |
RF / EM waves (in vacuum)
| Frequency | Wavelength | Band |
|---|---|---|
| 60 Hz | 5 000 km | Power line |
| 100 kHz | 3 km | LF / LORAN |
| 1 MHz | 300 m | AM broadcast |
| 10 MHz | 30 m | HF / shortwave |
| 27 MHz | 11 m | CB radio |
| 100 MHz | 3 m | FM broadcast |
| 433 MHz | 69 cm | ISM / key fobs |
| 915 MHz | 33 cm | LoRa (US), GSM |
| 2.4 GHz | 12.5 cm | WiFi, BT, microwave oven |
| 5 GHz | 6 cm | WiFi |
| 24 GHz | 1.25 cm | ISM / radar |
| 60 GHz | 5 mm | WiGig / WiFi 802.11ad |
| 300 GHz | 1 mm | mmWave / THz frontier |
Sound (air, 20 °C)
| Frequency | Wavelength |
|---|---|
| 20 Hz | 17.1 m |
| 100 Hz | 3.43 m |
| 440 Hz (A4) | 78 cm |
| 1 kHz | 34.3 cm |
| 4 kHz | 8.6 cm |
| 10 kHz | 3.43 cm |
| 20 kHz | 1.72 cm |
Notes
- Quarter-wave antenna length (m) ≈ 75 / f_MHz.
- In cable, velocity factor reduces the wavelength — typical coax VF ≈ 0.66.
- Speed of sound varies with temperature: v ≈ 331 + 0.6 · T(°C) m/s.
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