What formula is used?

The converter uses c = λf, where c is the speed of light in vacuum (299,792,458 m/s), λ is the wavelength in meters, and f is the frequency in Hz. Rearranged: f = c / λ and λ = c / f.

What range of wavelengths is visible to the human eye?

The human eye detects light roughly between 380 nm (violet) and 700 nm (deep red). This corresponds to frequencies of about 430 THz (red) to 790 THz (violet).

Why does the color swatch appear only for some inputs?

Colors are only shown when the computed wavelength falls within the visible spectrum (380–700 nm). Radio waves, microwaves, UV, X-rays, and gamma rays lie outside this range and have no associated perceived color.

Does this assume the speed of light in a vacuum?

Yes. The calculation uses c = 299,792,458 m/s (exact, per SI definition). In other media the phase velocity is slower (c/n), but this tool does not apply a refractive index — use it for free-space or vacuum calculations.

What is THz and why is it used?

THz (terahertz) equals 10¹² Hz. Visible light frequencies run from roughly 430 to 790 THz, so THz is a convenient unit — using plain Hz would produce 14-digit numbers. The tool displays both.

Wavelength Frequency Light Converter

Convert between wavelength and frequency for any electromagnetic radiation — enter nm, m, Hz, or THz and get all values instantly, with visible-spectrum color identification.

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Summary

This tool converts between wavelength and frequency for any electromagnetic radiation using the fundamental relation c = λf. Enter a value in nanometers, meters, hertz, or terahertz and the converter instantly computes all equivalent representations. For wavelengths in the visible range (380–700 nm) it also identifies the perceived color, making it useful for optics, spectroscopy, photonics, and physics coursework.

How it works

Enter a wavelength in nanometers or meters, or a frequency in Hz or THz.
The converter applies the formula c = λf (where c = 299,792,458 m/s).
All equivalent values are calculated and displayed simultaneously.
Wavelengths between 380 nm and 700 nm show the corresponding visible spectrum color.
Use the unit toggle to switch input mode between wavelength and frequency.

Use cases

Convert laser wavelengths (e.g., 532 nm green laser) to frequency.
Identify the visible color for a given wavelength or frequency.
Convert radio/microwave frequency bands to their wavelengths.
Cross-reference spectroscopy data between wavelength and frequency notations.
Check UV and infrared boundary frequencies in optical engineering.
Verify photon energy relationships for educational physics problems.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu