Wavelength to Frequency Converter
Common Conversions
| nm | Hz |
|---|---|
| 100 | 2998000000000000 |
| 200 | 1499000000000000 |
| 254 | 1180000000000000 |
| 400 | 749500000000000 |
| 500 | 599600000000000 |
| 600 | 499700000000000 |
| 700 | 428300000000000 |
| 1000 | 299800000000000 |
| 2000 | 149900000000000 |
| 5000 | 59960000000000 |
| 10000 | 29980000000000 |
| 100000 | 2998000000000 |
Why this conversion matters in chemistry
DNA-photolesion mechanistic work runs into this conversion routinely. A 260 nm DNA absorbance peak converts to 1.153 × 10¹⁵ Hz via ν = c/λ with c = 299,792,458 m/s exact — and from there to E = hν = 7.64 × 10⁻¹⁹ J = 4.77 eV per photon. The figure is what a biophysical-chemistry group compares against the energy threshold for pyrimidine (6-4) pyrimidone photoadduct formation. It sits at the handoff between nm-stated UV-Vis wavelength axes and the Hz form quantum photon-energy math actually uses.
Formula
Where the factor comes from
Nothing here was measured. The 1983 redefinition of the meter fixed the speed of light at 299,792,458 m/s and then built the length unit around that number, so c carries no uncertainty and never will — measuring it more carefully now only refines the meter. The relation λν = c holds for a wave in vacuum, and rearranging gives ν = c/λ. The unit algebra is a single prefix step: 299,792,458 m/s × 10⁹ nm/m = 2.99792458 × 10¹⁷ nm/s, so dividing that by a wavelength in nanometers returns hertz directly. Constant and prefix are both exact by definition, which makes the factor exact to every digit worth writing. What is not exact is the assumption of vacuum: in a medium the wave travels at c/n, and the relation becomes ν = c/(nλ).
Precision and significant figures
The factor contributes nothing, so the answer carries exactly the figures the wavelength brought. A benchtop UV-Vis reporting λmax to ±0.5 nm at 500 nm is good to about one part in a thousand, which supports three significant figures in the frequency and no more — 5.996 × 10¹⁴ Hz, not the fifteen digits a calculator offers. Round the mantissa and leave the exponent alone; the exponent is bookkeeping, not precision. At the other extreme the asymmetry reverses. Frequency is the quantity metrology pins hardest: optical frequencies are counted against a cesium-referenced comb to a relative uncertainty far below anything a grating delivers in nanometers, which is why reference line positions are published as frequencies and the wavelength is the derived number.
Worked Examples
About green light — the middle of the visible spectrum.
About violet light — the high-energy edge of visible.
About red light — the low-energy edge of visible.
About a UV germicidal wavelength — the Hg-lamp anchor.
Common mistakes
Air wavelengths fed into the vacuum relation
ν = c/λ takes a vacuum wavelength. Air at ordinary lab conditions has a refractive index near 1.00027 across the visible, so an air wavelength run through the bare relation overstates the frequency by roughly 270 parts per million — about 1.6 × 10¹¹ Hz at 500 nm. Immaterial for a broad solution band; disqualifying for anything compared against a published line position.
Band maxima move when the axis does
A spectrum is a distribution, and changing its axis requires the Jacobian: intensity per nanometer and intensity per hertz differ by a factor of λ²/c. Convert only the position of a broad emission maximum and the peak lands where it does not belong, sometimes by tens of nanometers. Narrow atomic lines are safe; fluorescence envelopes and lamp profiles are not.
Per-photon joules read as molar energy
E = hν returns the energy of a single photon. At 500 nm that is 3.97 × 10⁻¹⁹ J, a number with no business sitting beside a bond enthalpy. Multiply by the Avogadro constant to reach the molar scale — 239 kJ/mol for that same photon — before setting the figure against dissociation energies or activation barriers.