Frequency Of Light Calculator

Frequency of Light

Electromagnetic waves travel at the speed of light $c$ in vacuum. Frequency and wavelength are inversely related: shorter wavelength means higher frequency.

Formula

$$ f = \frac{c}{\lambda} \qquad c = 299{,}792{,}458\ \text{m/s} $$

Example: green light at 550 nm has $f = 2.998 \times 10^8 / (550 \times 10^{-9}) \approx 5.45 \times 10^{14}$ Hz, or about 545 THz.

How to Use This Calculator

Enter wavelength in angstroms, nanometers, micrometers, or other supported units. The tool returns frequency in Hz through THz using the exact speed of light.

Frequently Asked Questions

Why use the exact speed of light value?

The SI definition fixes c at 299792458 m/s exactly. Using this value gives consistent results for spectroscopy and optics calculations.

Does this work for light in glass or water?

This calculator uses vacuum c. In a medium, effective speed is c divided by the refractive index n, so frequency stays the same but wavelength shrinks.

What wavelength unit should I use for visible light?

Nanometers are standard. Violet is roughly 400 nm and red about 700 nm.

How do I convert THz to Hz?

Multiply by 10 to the 12. One terahertz equals one trillion hertz.

Is frequency the same as photon energy?

They are proportional: E equals h times f. Use a photon energy calculator when you need joules or electron-volts.

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Frequency Of Light Calculator