Wavelength and Frequency Calculator

Solve for

Medium

Wavelength

Frequency, Hz

Your own wave speed, m/s

Leave at 0 to use the medium's speed.

Result

Result599,584,900,000,000
What was calculatedFrequency, Hz
Frequency in readable units599.585 THz
Colour or bandgreen
Photon energy, eV2.4797
Wave speed, m/s299,792,458
Period, s0

Speed divided by one of the two

Converts wavelength to frequency and back for light, sound in air and sound in water, and gives the photon energy.

The relationship is simple: wave speed equals wavelength times frequency. Given the speed in a medium, either quantity follows from a division. The difficulty is scale: light is measured in terahertz, radio in megahertz, sound in hertz.

Speed depends on the medium and on the kind of wave. Light in vacuum travels 299,792,458 metres a second, sound in air 343, and in water nearly four and a half times faster. Which is why, underwater, the frequency stays put while the wavelength stretches.

What this calculator shows

Frequency or wavelength from the other one
Frequency in convenient units, from hertz up to terahertz
The colour for visible light and the photon energy in electronvolts

What to keep in mind

Light wavelengths are entered in nanometres and sound wavelengths in metres, as each is conventionally quoted.
Colour boundaries are conventional and the transitions are gradual; the visible range is taken as 380 to 750 nanometres.

FAQs

How are wavelength and frequency related?

Their product is the wave speed in the medium. Shorter wavelength means higher frequency, and the other way round.

How fast is sound in air?

343 metres a second at 20 degrees. It rises by roughly 0.6 metres a second for every degree warmer.

Which wavelength is which colour?

Violet around 400 nm, blue 470, green 530, yellow 580, orange 600, red 650 and above. The boundaries are conventional and the transitions gradual.

How do I calculate photon energy?

Multiply the frequency by Planck's constant. Converted to electronvolts, visible light spans roughly 1.6 to 3.3 eV.

Worked example

Green light

Input: A wavelength of 500 nm in vacuum

Output: 599.585 THz, photon energy 2.48 eV

Note: This is the middle of the visible range — the region the eye is most sensitive to. Which is no accident in high-visibility vests and laser pointers.

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Result

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