Math
Wavelength Calculator
Solve v = f x lambda for wavelength, frequency, or wave speed. Includes photon energy (J and eV) and EM band classification.
Wavelength Calculator
Given wave speed and frequency, compute lambda = v / f.
Sound presets are mechanical waves, so photon energy is not available for them. Photon energy mode always uses c (vacuum) to convert between frequency and wavelength.
Cycles per second. Must be greater than zero.
Wavelength
2.997925 m
Wave speed v
2.9979e+8 m/s
Frequency f
100 MHz
Wavelength lambda
2.997925 m
Period T
1.0000e-8 s
Angular frequency omega
6.2832e+8 rad/s
Wavenumber k
2.095845 1/m
Photon energy
6.6261e-26 J
Photon energy
4.1357e-7 eV
EM band
Radio
Frequently Asked Questions about the Wavelength Calculator
What is the wavelength formula?
v = f x lambda, where v is wave speed, f is frequency in hertz, and lambda is wavelength. For light in vacuum, v = c = 2.998 x 10^8 m/s. For sound in air at 20 C, v is about 343 m/s. Solve for any of the three given the other two.
What is the wavelength of visible light?
Visible light spans roughly 380 nm (violet) to 750 nm (red). Green light at 550 nm has a frequency of c / lambda = 2.998 x 10^8 / 5.50 x 10^-7 = 5.45 x 10^14 Hz, or 545 THz.
How do I calculate photon energy from wavelength?
E = h x c / lambda, where h is Planck's constant (6.626 x 10^-34 J s). For 550 nm green light: E = 6.626e-34 x 2.998e8 / 5.50e-7 = 3.61 x 10^-19 J, or 2.25 eV. The calculator does this automatically for any EM wave.
What EM band does my wavelength fall in?
Roughly: gamma rays below 0.01 nm, X-rays 0.01-10 nm, UV 10-380 nm, visible 380-750 nm, IR 0.75-1000 um, microwaves 1 mm-1 m, radio above 1 m. The calculator classifies the band so you can sanity-check your numbers.
Does wavelength change between media?
Yes. When light enters glass (n = 1.5), its speed drops to c / n and the wavelength drops by the same factor, but frequency stays the same. The calculator assumes vacuum/air by default. Override v if you are working inside a denser medium.