Calculate light frequency from wavelength using f = c/λ. Visible spectrum color mapping, photon energy in eV, wave number, and electromagnetic spectrum reference table.
The frequency of light is one of the most fundamental quantities in physics, connecting wave behavior to photon energy through quantum mechanics. Every color you see corresponds to a specific frequency of electromagnetic radiation — red light oscillates at roughly 430 THz while violet reaches nearly 790 THz.
This calculator instantly converts any wavelength of electromagnetic radiation into its corresponding frequency using the core relationship f = c/λ, where c is the speed of light in vacuum (299,792,458 m/s). It supports wavelengths from radio waves to gamma rays, and accounts for different media through the refractive index input.
Beyond frequency, the tool computes photon energy in both joules and electron-volts (eV), the wave number used in spectroscopy, and the number of photons emitted per second at a given power level. A color-coded visible spectrum map instantly shows where your wavelength falls. Whether you are a physics student studying optics, an engineer designing laser systems, or a spectroscopist analyzing emission lines, this calculator eliminates tedious unit conversions and delivers all key quantities simultaneously.
Converting between wavelength and frequency involves large exponents and easy-to-confuse unit prefixes (nm, μm, THz, GHz). A single misplaced decimal can throw your answer off by orders of magnitude. This calculator handles all unit conversions automatically, computes derived quantities like photon energy and wave number in one step, and visually maps wavelengths to the visible spectrum for instant identification. It is invaluable for optics labs, spectroscopy analysis, and physics coursework.
Frequency of Light: f = c / λ (in vacuum) f = v / λ where v = c / n (in a medium) Photon Energy: E = hf = hc / λ Wave Number: k = 1 / λ Where: c = 299,792,458 m/s (speed of light) h = 6.626 × 10⁻³⁴ J·s (Planck constant) n = refractive index of medium λ = wavelength in meters
Result: 5.451 × 10¹⁴ Hz (545.1 THz)
A 550 nm wavelength (green light) in vacuum has frequency f = 299,792,458 / (550 × 10⁻⁹) ≈ 5.451 × 10¹⁴ Hz or about 545.1 THz. Its photon energy is approximately 2.25 eV.
The electromagnetic spectrum spans an enormous range of frequencies, from radio waves with frequencies below 300 MHz to gamma rays exceeding 30 exahertz. Visible light occupies only a narrow band between roughly 430 and 790 THz, yet this tiny slice powers photosynthesis, human vision, and optical communications. Understanding where a given wavelength falls on the spectrum matters for applications ranging from medical imaging (X-rays) to telecommunications (microwaves and infrared).
Einstein demonstrated that light consists of quantized packets of energy called photons, where each photon carries energy E = hf. This relationship bridges wave optics and quantum mechanics — the color of light is not just a wave property but determines the energy delivered per photon. This principle underpins the photoelectric effect, laser design, photovoltaic cells, and spectroscopic analysis of atoms and molecules.
Fiber-optic communications use infrared wavelengths (1310 nm and 1550 nm) where glass fiber has minimum attenuation. LED and laser design requires matching photon energy to semiconductor band gaps. Medical applications use specific UV wavelengths for sterilization and phototherapy. In all these cases, converting between wavelength, frequency, and energy is essential for system design and performance optimization.
Frequency and wavelength are inversely proportional: f = c/λ. Higher frequency means shorter wavelength and higher energy. Visible light frequencies range from about 430 THz (red) to 790 THz (violet).
No. When light enters a medium like glass or water, its speed and wavelength decrease but its frequency stays the same. This is why dispersion occurs — different frequencies (colors) are refracted by different amounts.
Use f(THz) = 299,792.458 / λ(nm). For example, 500 nm corresponds to 299,792.458 / 500 ≈ 599.6 THz.
Photon energy in eV equals E = 1240 / λ(nm). For a 620 nm red photon, E = 1240/620 = 2.0 eV. This shortcut works because hc ≈ 1240 eV·nm.
Wave number (k = 1/λ) measures the number of wave cycles per unit distance. Spectroscopists prefer cm⁻¹ because it is directly proportional to energy and frequency, making spectral comparisons intuitive.
It depends on wavelength. For a 532 nm green laser at 1 mW: E_photon = hc/λ ≈ 3.73 × 10⁻¹⁹ J. Photons/s = 0.001 / 3.73 × 10⁻¹⁹ ≈ 2.68 × 10¹⁵ photons per second.