Light, sound and radio signal conversion — frequency, wavelength, speed.
| Name | Wavelength (nm) | Frequency (THz) | Energy (eV) | Note |
|---|---|---|---|---|
| Gamma rays | < 0.01 | > 3×10⁷ | > 124 keV | Nuclear reactions |
| X-rays | 0.01–10 | 30,000–30,000,000 GHz | 0.1–124 keV | Medical imaging |
| UV-C | 100–280 | 1,070–3,000 | 4.4–12.4 | Germicidal |
| UV-B | 280–315 | 952–1,070 | 3.9–4.4 | Sunburn |
| UV-A | 315–400 | 750–952 | 3.1–3.9 | Tanning, blacklight |
| Violet | 380–450 | 666–789 | 2.75–3.26 | Visible |
| Blue | 450–495 | 606–666 | 2.51–2.75 | Visible |
| Green | 495–570 | 526–606 | 2.18–2.51 | Visible |
| Yellow | 570–590 | 508–526 | 2.10–2.18 | Visible |
| Orange | 590–620 | 484–508 | 2.00–2.10 | Visible |
| Red | 620–750 | 400–484 | 1.65–2.00 | Visible |
| Near IR (NIR) | 750–1,400 | 214–400 | 0.89–1.65 | Remote control, fibre |
| Short IR (SWIR) | 1,400–3,000 | 100–214 | 0.41–0.89 | LiDAR, night vision |
| Mid IR (MWIR) | 3,000–8,000 | 37.5–100 | 0.16–0.41 | Thermal imaging |
| Far IR / THz | 8,000–1,000,000 | 0.3–37.5 | <0.16 | Body scanners |
| — Common Lasers — | ||||
| CO₂ laser | 10,600 nm | 28.3 THz | 0.12 eV | Cutting, surgery |
| Nd:YAG | 1,064 nm | 281 THz | 1.17 eV | Industrial, medical |
| Ruby laser | 694 nm | 432 THz | 1.79 eV | First laser (1960) |
| HeNe laser | 632.8 nm | 474 THz | 1.96 eV | Barcode scanners |
| GaN blue laser | 405 nm | 741 THz | 3.06 eV | Blu-ray |
| Fibre optic (SMF) | 1,310 nm | 229 THz | 0.95 eV | Telecom O-band |
| Fibre optic (C-band) | 1,550 nm | 193 THz | 0.80 eV | Telecom, lowest loss |
c = 299,792,458 m/s in vacuum. λ = c / f. E = h·f (h = 6.626×10⁻³⁴ J·s).
| Medium | Speed (m/s) | Condition | Note |
|---|---|---|---|
| Air | 343 | 20°C, 1 atm | ~1 km per 3 sec |
| Air | 331 | 0°C | Increases ~0.6 m/s per °C |
| Helium | 972 | 20°C | High-pitched voice effect |
| Hydrogen | 1,270 | 20°C | Fastest gas |
| Fresh water | 1,480 | 20°C | ~4× faster than air |
| Sea water | 1,520 | 20°C | Depth-dependent |
| Ice | 3,200 | 0°C | Glaciology applications |
| Wood (oak) | 3,850 | — | Varies by species |
| Concrete | 3,000–4,000 | — | Structural testing |
| Aluminium | 6,320 | — | Ultrasonic NDT |
| Steel | 5,100–5,900 | — | Pipe inspection |
| Glass | 5,640 | — | Window glass |
| Diamond | 12,000 | — | Hardest natural material |
| Sound | dB SPL | Note |
|---|---|---|
| Threshold of hearing | 0 dB | Reference level |
| Breathing | 10 dB | Barely audible |
| Quiet room | 30 dB | Library |
| Normal conversation | 60 dB | 1 metre distance |
| Traffic | 70–80 dB | Busy street |
| Concert | 100–110 dB | Hearing damage risk |
| Jet engine (30m) | 140 dB | Pain threshold |
Human hearing: 20 Hz – 20 kHz. Ultrasound: >20 kHz. Infrasound: <20 Hz.
| Band | Abbr | Frequency | Wavelength | Use |
|---|---|---|---|---|
| Extremely Low Freq. | ELF | 3–30 Hz | 100,000–10,000 km | Submarine comms |
| Super Low Freq. | SLF | 30–300 Hz | 10,000–1,000 km | Submarine comms |
| Very Low Freq. | VLF | 3–30 kHz | 100–10 km | Navigation, time signals |
| Low Freq. | LF | 30–300 kHz | 10–1 km | AM radio longwave |
| Medium Freq. | MF | 300 kHz–3 MHz | 1,000–100 m | AM radio, maritime |
| High Freq. | HF | 3–30 MHz | 100–10 m | Shortwave, amateur radio |
| Very High Freq. | VHF | 30–300 MHz | 10–1 m | FM radio, TV, aviation |
| Ultra High Freq. | UHF | 300 MHz–3 GHz | 1 m–10 cm | TV, 4G LTE, Wi-Fi 2.4GHz |
| Super High Freq. | SHF | 3–30 GHz | 10–1 cm | Wi-Fi 5GHz, radar, 5G |
| Extremely High Freq. | EHF | 30–300 GHz | 10–1 mm | 5G mmWave, imaging |
| Terahertz | THz | 300 GHz–3 THz | 1 mm–100 μm | Security screening |
| — Common Wireless — | ||||
| Wi-Fi 2.4 GHz (802.11n) | 2.4–2.484 GHz | 12.5 cm | Range: ~50m indoor | |
| Wi-Fi 5 GHz (802.11ac) | 5.15–5.85 GHz | 5.8 cm | Range: ~30m indoor | |
| Wi-Fi 6 GHz (802.11ax) | 5.925–7.125 GHz | 4.7 cm | Wi-Fi 6E | |
| Bluetooth | 2.402–2.480 GHz | 12.4 cm | FHSS, 79 channels | |
| GPS L1 | 1,575.42 MHz | 19.0 cm | Navigation | |
| 4G LTE Band 1 | 2,110–2,170 MHz | 13.7 cm | Downlink | |
| 5G NR Sub-6GHz | 600 MHz–6 GHz | 50–5 cm | Wide coverage | |
| 5G mmWave | 24.25–52.6 GHz | 12–5.7 mm | High speed, short range | |
