Pick any one of wavelength, frequency, or energy as your starting point in the Calculate From field, enter your value and unit, and the Wavelength Frequency Energy Converter will solve for the other two — giving you results in wavelength, frequency, eV, and joules all at once.
Wavelength
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Frequency
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Energy (eV)
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Energy (Joules)
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To calculate photon energy from wavelength, use Planck's equation: E = hc/λ, where h is Planck's constant (6.626 × 10⁻³⁴ J⋅s), c is the speed of light (3 × 10⁸ m/s), and λ is the wavelength in meters.
Convert the wavelength to meters, then apply E = hc/λ. For example, for 550 nm light: convert to 550 × 10⁻⁹ m, then calculate E = (6.626 × 10⁻³⁴ × 3 × 10⁸) / (550 × 10⁻⁹) = 3.61 × 10⁻¹⁹ J.
First calculate energy in joules using E = hc/λ, then convert to electronvolts by dividing by the elementary charge (1.602 × 10⁻¹⁹ C). Alternatively, use the direct formula: E(eV) = 1240/λ(nm).
Frequency and wavelength are inversely related by the speed of light: c = λf, where c is the speed of light, λ is wavelength, and f is frequency. Higher frequency means shorter wavelength.
A 100 nm photon has an energy of approximately 12.4 eV or 1.99 × 10⁻¹⁸ joules. This is in the ultraviolet range of the electromagnetic spectrum.
Visible light: 380-700 nm, UV: 10-380 nm, infrared: 700 nm-1 mm, radio waves: 1 mm-100 km, X-rays: 0.01-10 nm, gamma rays: <0.01 nm.
Planck's constant (h = 6.626 × 10⁻³⁴ J⋅s) is fundamental to quantum mechanics and relates the energy of a photon to its frequency or wavelength. It's the proportionality constant in Planck's equation E = hf.