wavelengthsoptical

Optical wavelengths are wavelengths of electromagnetic radiation in the portion of the spectrum used by human vision and by a wide range of optical devices. In vacuum, wavelength λ and frequency f are linked by c = λ f, so the wavelength is the speed of light divided by the frequency. In materials, light slows and its wavelength shortens according to λ = λ0 / n, where n is the refractive index of the medium for that wavelength.

The visible range for most humans spans roughly 380 to 750 nanometers, with shorter wavelengths appearing violet and longer ones red; wavelengths outside this range are associated with ultraviolet (below about 380 nm) and infrared (above about 750 nm). Perception of color is not only determined by wavelength but also by the spectral power distribution and the eye's response.

Optical wavelengths are central to imaging, spectroscopy, and communications. In the near-infrared, approximately 750–2500 nm, many sensors and fiber optic systems operate; standard telecom wavelengths around 1310 nm and 1550 nm minimize attenuation in silica fibers. Shorter visible wavelengths are used in laser pointers, lighting, and microscopy; ultraviolet wavelengths are used for sterilization and lithography, though high-energy UV requires special materials and safety considerations.

Measurement and control of optical wavelengths rely on spectrometers, interferometers, frequency combs, and calibrated light sources. Dispersion causes wavelength-dependent phase and group velocity in materials, a key factor in lenses and prisms. Wavelength selection is achieved with filters, gratings, crystals, and optical fibers.