Calculate photon wavelength, frequency, and energy interchangeably. Convert between nm, eV, THz, and wavenumber with electromagnetic spectrum visualization.
Photons are quantum packets of electromagnetic radiation characterized by wavelength, frequency, and energy — all interrelated by Planck's equation. The Wavelength of Photon Calculator converts seamlessly between these units and places your photon on the electromagnetic spectrum, from radio waves to gamma rays.
The fundamental relationship E = hf = hc/λ links photon energy (E), frequency (f), and wavelength (λ) through Planck's constant (h) and the speed of light (c). A photon with 500 nm wavelength (green light) has a frequency of 600 THz and energy of 2.48 eV. This single relationship governs all of photophysics, from laser design to spectroscopy to semiconductor band gaps.
This calculator handles all common units: wavelength in nm, μm, or m; frequency in Hz, THz, or GHz; energy in eV, J, or kJ/mol; and wavenumber in cm⁻¹ (commonly used in IR spectroscopy). It identifies the spectral region, shows visible light color, and includes presets for common spectral lines, laser wavelengths, and absorption edges.
Use this calculator when you need to move between photon wavelength, frequency, energy, and wavenumber without doing Planck-equation algebra by hand. It is useful in spectroscopy, photonics, and semiconductor work where spectral units are swapped constantly. The conversion table also makes it easier to compare a line or laser wavelength against the visible spectrum at a glance.
E = hf = hc/λ. h = 6.626 × 10⁻³⁴ J·s = 4.136 × 10⁻¹⁵ eV·s. c = 2.998 × 10⁸ m/s. λ = c/f. ν̃ = 1/λ (wavenumber, cm⁻¹). E(eV) = 1240 / λ(nm).
Result: f = 563.5 THz, E = 2.330 eV, ν̃ = 18,797 cm⁻¹ (visible green)
A 532 nm photon (Nd:YAG laser second harmonic) has frequency 563.5 THz and energy 2.330 eV. This falls in the green portion of the visible spectrum (495-570 nm). The wavenumber 18,797 cm⁻¹ is often used for Raman spectroscopy calculations.
The electromagnetic spectrum spans over 15 orders of magnitude in wavelength: from radio waves (km) through microwaves (cm), infrared (μm), visible light (nm), ultraviolet (nm), X-rays (pm), to gamma rays (fm). Each region has distinct sources, detectors, and applications.
The visible window (380-700 nm) is a tiny fraction of the spectrum but enormously important — evolution tuned human vision to the peak of solar emission. Our atmosphere is transparent to visible light and radio waves, but absorbs most UV, IR, and X-rays, shaping both biology and astronomy.
Radio (>1 mm): Communications, radar, radio astronomy. Microwave (1-300 mm): WiFi, microwave ovens, cosmic background radiation. Infrared (700 nm-1 mm): Thermal imaging, fiber optics, spectroscopy, remote controls. Visible (380-700 nm): Human vision, photography, displays, solar cells. UV (10-380 nm): Sterilization, lithography, fluorescence. X-ray (0.01-10 nm): Medical imaging, crystallography, security screening.
Planck's equation E = hf represents one of the foundational results of quantum mechanics. The photoelectric effect (Einstein, 1905) demonstrated that light comes in discrete energy packets — photons. The photon energy E = hf explained why ultraviolet light ejects electrons from metals but visible light doesn't, regardless of intensity. This directly led to quantum mechanics and the wave-particle duality of light.
Use the shortcut: Energy (eV) = 1240 / Wavelength (nm). So 620 nm red light = 2.0 eV, and 310 nm UV = 4.0 eV. This comes from hc = 1240 eV·nm.
Visible light spans roughly 380 nm (violet) to 700 nm (red). Peak human sensitivity is at 555 nm (green-yellow). Below 380 nm is ultraviolet; above 700 nm is infrared. The boundaries are not sharp — sensitivity tapers gradually.
Wavenumber (ν̃ = 1/λ, in cm⁻¹) is proportional to energy and widely used in IR and Raman spectroscopy. It's convenient because it increases with energy (unlike wavelength which decreases), and the numbers are manageable: visible light is 14,000-26,000 cm⁻¹, mid-IR is 400-4,000 cm⁻¹.
UV-A (315-400 nm): 3.1-3.9 eV. UV-B (280-315 nm): 3.9-4.4 eV. UV-C (100-280 nm): 4.4-12.4 eV. UV-C is germicidal because its photon energy exceeds DNA bond strengths (~4.9 eV). Ozone absorbs UV-C in the atmosphere.
LED wavelength is determined by the semiconductor band gap. GaAs emits at ~870 nm (IR), GaP at ~565 nm (green), InGaN ranges from 365-520 nm (UV to green). Blue LEDs (InGaN, ~450 nm, Nobel Prize 2014) enabled white LED lighting via phosphor conversion.
A photon's energy equals kT at a specific temperature: T = E/k, where k = 86.17 μeV/K (Boltzmann constant). A 2.5 eV visible photon corresponds to ~29,000 K — the surface temperature needed for thermal emission to peak at that energy. Room temperature (300 K) corresponds to about 26 meV (infrared thermal radiation).