Frequency of Light Calculator

Light is an electromagnetic wave, and its frequency is linked to its wavelength by the speed at which the wave travels. In a vacuum, the speed of light is exactly 299,792,458 meters per second. Frequency equals that speed divided by wavelength in meters. A wavelength of 500 nanometers is 0.0000005 meter, producing a frequency of 599,584,916,000,000 hertz, or about 599.585 terahertz. This calculator performs that conversion and reports both hertz and terahertz. Wavelength is the distance between corresponding points on successive waves, such as crest to crest. Frequency is the number of wave cycles passing a point each second. Because their product equals wave speed, wavelength and frequency vary inversely: shorter wavelengths have higher frequencies, while longer wavelengths have lower frequencies. Visible light occupies only a small part of the electromagnetic spectrum, approximately 380 to 750 nanometers. Ultraviolet radiation has shorter wavelengths and higher frequencies; infrared and radio waves have longer wavelengths and lower frequencies. Nanometers are convenient for visible and nearby optical wavelengths because one nanometer is one billionth of a meter. Meters are useful for long radio waves and general SI calculations. The tool converts nanometers internally before applying the formula. Terahertz means one trillion hertz and gives optical frequencies a more readable scale. Results assume propagation in a vacuum. In air the speed is slightly lower, and in glass, water, or another material it is reduced according to that material's refractive index. Frequency normally remains unchanged when light crosses from one medium into another, while speed and wavelength change together. For that reason, use the vacuum wavelength when comparing standard spectral lines or photon frequencies unless a problem explicitly provides wavelength inside a medium. Measurement precision also matters: an input rounded to a whole nanometer does not justify every displayed output digit. Round the final answer appropriately for laboratory work. The formula applies across the electromagnetic spectrum, from radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, as long as wavelength is positive and expressed consistently.