What is the wave equation?

v = fλ for any wave. For light in vacuum, v = c ≈ 3 × 10⁸ m/s, so c = fλ.

What is the energy of a photon?

E = hf = hc/λ, where h = 6.626 × 10⁻³⁴ J·s is Planck's constant. Visible photons have energy 1.7 to 3.3 eV.

What is the visible spectrum range?

Roughly 400 to 700 nm (violet to red), corresponding to frequencies of 4.3 × 10¹⁴ to 7.5 × 10¹⁴ Hz.

Does the formula work for sound waves?

Yes, with v = the speed of sound in the medium (about 340 m/s in air). Just set the wave speed accordingly.

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NSW · HSCModule 7

Wavelength, frequency and photon energy calculator

c = fλ and E = hf in one click. Defaults are for light in vacuum; change the wave speed for sound or other media.

Inputs

Solve forWavelength λ (m)Visible light: 4e-7 to 7e-7 mWave speed (m/s)Light in vacuum: c ≈ 2.998e+8 m/s

Result

Frequency f

5.996e+14Hz

Wavelength λ

5.000e-7m

Photon energy E = hf

3.973e-19J

Photon energy

2.480eV

c = fλ for electromagnetic waves; E = hf for a photon.

How this calculator works

Pick which variable you want to solve for, enter the other, and the calculator applies c = fλ. The result panel also shows the photon energy in joules and electron-volts.

Common questions

What is the wave equation?: v = fλ for any wave. For light in vacuum, v = c ≈ 3 × 10⁸ m/s, so c = fλ.
What is the energy of a photon?: E = hf = hc/λ, where h = 6.626 × 10⁻³⁴ J·s is Planck's constant. Visible photons have energy 1.7 to 3.3 eV.
What is the visible spectrum range?: Roughly 400 to 700 nm (violet to red), corresponding to frequencies of 4.3 × 10¹⁴ to 7.5 × 10¹⁴ Hz.
Does the formula work for sound waves?: Yes, with v = the speed of sound in the medium (about 340 m/s in air). Just set the wave speed accordingly.