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In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC. UV is the lowest energy range energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.
The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.
In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. [4] [5] In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization.
A photon has an energy, E, proportional to its frequency, f, by = = where h is the Planck constant, is the wavelength and c is the speed of light. This is sometimes known as the Planck–Einstein equation. [31]
The 41.8% point is the wavelength-frequency-neutral peak (i.e. the peak in power per unit change in logarithm of wavelength or frequency). These are the points at which the respective Planck-law functions 1 / λ 5 , ν 3 and ν 2 / λ 2 , respectively, divided by exp ( hν / k B T ) − 1 attain their maxima.
For example, a wavenumber in inverse centimeters can be converted to a frequency expressed in the unit gigahertz by multiplying by 29.979 2458 cm/ns (the speed of light, in centimeters per nanosecond); [5] conversely, an electromagnetic wave at 29.9792458 GHz has a wavelength of 1 cm in free space.
As UVA light is absorbed by the ocular media (lens and cornea), it may fluoresce and be released at a lower energy (longer wavelength) that can then be absorbed by the opsins. For example, when the lens absorbs 350 nm light, the fluorescence emission spectrum is centered on 440 nm. [29]
Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower its energy.