How to Use Light Frequency Calculator
The Light Frequency Calculator converts between three equivalent ways to describe electromagnetic radiation: wavelength, frequency, and photon energy.
- Choose what you know - Wavelength (nm, μm, m, Å, …), frequency (THz, GHz, MHz, Hz), or photon energy (eV, J). The Light Frequency Calculator solves for all other quantities.
- Optionally set the medium - Enter the refractive index n if you are working in glass (n ~ 1.5), water (n ~ 1.33), or another medium; leave blank (n = 1) for vacuum or air.
- Read every other quantity - The Light Frequency Calculator returns wavelength, frequency, and photon energy with consistent units. The frequency is unchanged by the medium; only the wavelength changes.
- Use the spectral band label - The calculator identifies the electromagnetic band (radio, microwave, IR, visible, UV, X-ray) so you can quickly see which technology domain your wavelength falls in.
Formula & Theory - Light Frequency Calculator
The Light Frequency Calculator is built on the three equivalent EM relations:
c = λ · f
v = c / n (phase speed in medium)
E = h · f = h c / λ| Symbol | Meaning |
|---|---|
| c | Speed of light in vacuum 299 792 458 m/s |
| n | Refractive index of medium |
| λ | Wavelength |
| f | Frequency |
| E | Photon energy |
| h | Planck constant |
Electromagnetic Spectrum Reference
| Band | Wavelength range | Frequency range |
|---|---|---|
| AM radio | ~300 m | ~1 MHz |
| WiFi (5 GHz) | ~6 cm | 5 GHz |
| Visible light | 380–700 nm | 430–790 THz |
| UV-C | 100–280 nm | 1.07–3 PHz |
| X-ray | 0.01–10 nm | 30 PHz–30 EHz |
Assumptions and Limits
The calculator assumes monochromatic, plane-wave radiation. For dispersive media, n depends on λ; enter the n that matches your operating wavelength. Group velocity differs from phase velocity in dispersive media — for pulse propagation, use group index instead.
Use Cases for Light Frequency Calculator
The Light Frequency Calculator is useful when you need a quick, transparent calculation for optics, photonics, and EM engineering:
- Spectroscopy - Convert spectral lines between wavelength, frequency, and energy units to compare results from different spectrometers or databases.
- Fiber optics - Compute the exact frequency channel around 1550 nm and verify its position on the ITU-T DWDM grid with 50 GHz or 100 GHz spacing.
- Communications engineering - Convert RF or microwave channel center frequencies to wavelengths and vice versa for antenna sizing and propagation modeling.
- Photovoltaics - Find the photon energy at a target absorption wavelength to assess whether it exceeds the semiconductor band gap.
- Laser selection - Quickly cross-reference laser line wavelengths (e.g., 532 nm, 1064 nm, 1550 nm) with their photon energies for nonlinear-optics and spectroscopy design.
- Medical and safety - Determine whether a given UV wavelength (e.g., 254 nm germicidal) corresponds to an energy sufficient to cause DNA damage (above ~4 eV).
For broadband signals, repeat the conversion at the edges of your spectrum. The Light Frequency Calculator works on monochromatic values and gives exact conversions for any point in the EM spectrum.