The equation
Formula and assumptions
f = c / λ · E = hf = hc / λ
This calculator assumes electromagnetic radiation traveling in vacuum.
Worked examples
See the method in practice
01
Visible light
A 500 nm photon has a frequency of about 5.996 × 10¹⁴ Hz.
02
Photon energy
The same 500 nm photon carries about 3.973 × 10⁻¹⁹ J, or 2.480 eV.
Questions
Frequently asked
Does light slow down in matter?
Yes. This tool uses the defined speed of light in vacuum; wavelength changes inside a medium.
Is photon energy proportional to wavelength?
It is inversely proportional: shorter wavelength means higher frequency and energy.
Sources & review
Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.
NIST CODATA fundamental constantsWritten by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology