Wave Calculator
Convert between frequency, wavelength, period and wave speed for sound, light and any medium, with photon energy, the Doppler shift and the harmonic series.
Last reviewed by the Radiatus Cloud team
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Speed connects frequency and wavelength, and the speed depends on the medium
Wave speed equals frequency times wavelength, which means that for a given medium the two are inversely related: doubling the frequency halves the wavelength. What changes when a wave crosses into a new medium is the speed and the wavelength, while the frequency stays the same, because frequency is set by the source. This is why sound entering water keeps its pitch while its wavelength quadruples, and why light bends at a boundary.
Sound and light differ in almost every respect
Sound is a pressure variation needing a medium and travelling at roughly 343 metres per second in air. Light is an electromagnetic wave needing no medium at all and travelling at about 300 million metres per second, nearly a million times faster. A frequency that produces a wavelength of a few metres in sound produces one of hundreds of kilometres in light, which is why the same numbers describe completely different physical situations.
Energy per photon depends only on frequency
The energy of a single photon is Planck's constant times frequency, so blue light carries more energy per photon than red regardless of how bright either is. Brightness is the number of photons; energy per photon is the colour. This is why ultraviolet damages skin and infrared does not, however intense the infrared: below a threshold frequency, no individual photon carries enough energy to do the damage, and adding more of them does not help.
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Frequently Asked Questions
What changes when a wave enters a new medium?
The speed and the wavelength change; the frequency does not, because it is set by the source. This is why sound entering water keeps its pitch while its wavelength quadruples.
Why is frequency inversely related to wavelength?
Because their product is the wave speed, which is fixed for a given medium. Doubling the frequency in the same medium necessarily halves the wavelength.
Why does ultraviolet damage skin when infrared does not?
Because photon energy depends on frequency alone. Below a threshold, no single photon carries enough energy to break the bond, and adding more photons by increasing brightness does not change what any one of them can do.
What is the difference between period and frequency?
They are reciprocals: period is the time for one cycle and frequency is cycles per second. A 50 Hz wave has a period of 20 milliseconds.
Does the Doppler effect change the wavelength or the frequency?
Both, in the observed wave. The source emits at a fixed frequency and the motion compresses or stretches the wavefronts, so the observer measures a different frequency and a different wavelength while the speed stays the same.
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How to Use
Enter any two wave properties to calculate the rest.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.