BYTETOOLS

Wavelength and Frequency Calculator

Convert between wavelength and frequency using c = λf, with wave speed for vacuum, a medium, sound in air or a custom value, plus photon energy in eV.

599.584916 THz
Frequency
1.668e-15 s
Period
2.4797 eV
Photon energy
Visible light — green
Spectrum band

c = λ · f

  • f = v ÷ λ = 299,792,458 m/s ÷ 5.0000e-7 m = 5.99585e+14 Hz
  • Wave speed = c = 299,792,458 m/s (light in vacuum, exact by definition).
  • Period T = 1 ÷ f = 1.66782e-15 s.
  • Wavenumber = 1 ÷ λ = 2.00000e+6 m⁻¹ = 20,000 cm⁻¹.
  • Photon energy E = h·f = 3.97289e-19 J = 2.479684 eV (electromagnetic radiation only).
  • Equivalent wavelength in vacuum = c ÷ f = 5.00000e-7 m = 500 nm → Visible light — green.
  • Angular frequency ω = 2πf = 3.76730e+15 rad/s.

Frequency is set by the source and never changes when a wave enters a new material — the wavelength is what shortens, because the speed drops to c/n. The spectrum band above is therefore worked out from the vacuum wavelength c ÷ f. Photon energy E = hf applies to electromagnetic radiation; it has no meaning for a sound wave. A 500 nm green photon carries 3.97 × 10⁻¹⁹ J, which is 2.48 eV.

What is the Wavelength and Frequency Calculator?

Wavelength and frequency are linked by c = λ·f, so f = c ÷ λ and λ = c ÷ f. In a vacuum light travels at exactly 299,792,458 m/s, which makes a 500 nm green wave 599.6 THz.

  • Converts wavelength to frequency and back with v = λ·f
  • Wave speed from vacuum, a refractive index, sound in air or a custom value
  • Photon energy E = hf reported in joules and electronvolts
  • Period, wavenumber in m⁻¹ and cm⁻¹, and angular frequency ω = 2πf
  • Names the spectrum band from radio through visible colours to gamma rays
  • Fully client-side — nothing you enter is uploaded

How to use the Wavelength and Frequency Calculator

  1. 1

    Choose whether to find frequency from wavelength or wavelength from frequency.

  2. 2

    Pick the wave speed: light in vacuum, light in a medium, sound in air, or a custom speed.

  3. 3

    If you chose a medium, select it from the list so the tool can apply v = c ÷ n.

  4. 4

    Enter your known value and set its unit, from picometres to kilometres or hertz to petahertz.

  5. 5

    Read the answer, the period, the photon energy in eV and the spectrum band, then copy the working.

About the Wavelength and Frequency Calculator

The ByteTools Wavelength and Frequency Calculator converts either way using v = λ·f. The wave speed can be light in a vacuum at exactly 299,792,458 m/s, light slowed inside a medium as c ÷ n with presets for water, glass, fused silica and diamond, sound in dry air at 343 m/s, or any custom speed you type in for sound in water, along a rail, or on a string.

Every answer arrives with the period T = 1 ÷ f, the wavenumber 1 ÷ λ in both m⁻¹ and cm⁻¹, the angular frequency 2πf, and the photon energy E = h·f in joules and electronvolts. The tool also names the part of the electromagnetic spectrum the wave belongs to, worked out from the equivalent vacuum wavelength rather than the in-medium one.

Wavelength units run from kilometres down to picometres, and frequency from hertz up to petahertz, so radio, microwave, infrared, visible, ultraviolet and X-ray problems all fit. Every calculation runs locally in your browser, with nothing uploaded and no history kept, and the page works offline once it has loaded.

Frequently asked questions

How do you convert wavelength to frequency?

Divide the wave speed by the wavelength: f = v ÷ λ. For light in a vacuum that means f = 299,792,458 ÷ λ, so a 500 nm green wave has a frequency of about 599.6 THz.

Does frequency change when light enters glass?

No. Frequency is fixed by the source and stays the same in every medium, while the speed drops to c ÷ n and the wavelength shortens by the same factor. That is why this tool works the spectrum band out from the equivalent vacuum wavelength.

How do you calculate the energy of a photon?

Photon energy is E = h·f, or equivalently E = hc ÷ λ, using Planck's constant. A 500 nm green photon carries 3.97 × 10⁻¹⁹ J, which is 2.48 electronvolts.

What is the wavelength of a 100 MHz FM radio signal?

Dividing the speed of light by the frequency gives 299,792,458 ÷ 100,000,000, which is about 3 metres. That is why FM aerials are around 75 cm long — a quarter of the wavelength.

Which speed of sound does this use?

The sound option uses 343 m/s, the value for dry air at 20 °C. Sound speed rises with temperature by roughly 0.6 m/s per °C and differs greatly in other materials, so use the custom speed box for water at about 1480 m/s or steel at about 5100 m/s.

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