Light is ‘radiant’ solar energy within a spectrum of Electro-Magnetic-Radiation (EMR). The EMR we can see is visible light and starts with Ultra Violet-Blue (UVB) at 380nm on a continuum to Red (R) at 620 nm to Extreme Red (ER) beyond our sight capacity at 750 nm. Just under the visible light spectrum are ‘too-short-to-see’ wavelengths that are ‘bluer-than-blue’ or ultra-violet; and just beyond the visible light spectrum are ‘too-long-to-see’ EMR wavelengths that are ‘redder-than-red’ or infrared.
Red Light is that part of the visible EMR Spectrum that ranges from approximately 620nm to 700nm (from an orange-red to an extreme-deep or far-red). We must take into account that the wavelengths are not sharply defined and overlap one another.
Beyond around 750nm the EMR becomes invisible becoming Infrared wavelengths. The science of infrared thermography has adopted more modern terminology with terms such as Near Infrared (NIR) from 750 nm to 3.0 µm; then Mid Infrared (MIR) from 3.0 µm to 5.0 µm; and then Far Infrared (FIR) from 5.0 µm to 15.0 µm. Keep in mind that thermal radiation (heat) can be delivered throughout the entire EMR spectrum but the thermal carrying intensity is highest in the Infrared (IR) ‘band’.
When living tissue is irradiated by ‘light’, tiny ‘quanta’s or particles’ of light called photons are either scattered or absorbed by the tissue. This is dependent on the wavelength. Red spectra wavelengths penetrate and are absorbed the most. It’s an interesting curiosity that the biological tissue of both plants and people use the same portion of the 650 – 950 nm spectrum to activate cellular redox reactions.
“Oxidation-reduction reactions (or redox) reactions, are a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron”
Source: Chemwiki http://chemwiki.ucdavis.edu/
When a quantum or a ‘beam’ of photons travelling at the speed of light impacts on living tissue the quanta-waves ‘concertina’ together changing their state and become particles imparting the energy of the wavelengths (as all the photons concertina together) into the tissue. This is because light exhibits the properties of both waves and particles. This property was referred to by Einstein as the wave–particle duality, therefore a photon is really a ‘wavicle’.
Harvard Medical School researcher Michael Hamblin points out that,
The photons that are absorbed interact with an organic molecule or chromophore located within the tissue. Because these photons have wavelengths in the red or NIR regions of the spectrum, the chromophores that absorb these photons tend to have delocalized electrons in molecular orbitals that can be excited from the ground state to the first excited state by the quantum of energy delivered by the photon. (Hamblin PhD)
“Every cell in the body has ‘red-light’ sensitivity. Photosensitive chemicals called ‘cytochromes’ are concentrated within the energy generating compartments called mitochondria. When these chemicals are stimulated with the correct wavelength, dose and power it starts an energy cascade that causes the cells to grow, regenerate, repair and heal” (Whelen 2005).
In this way Phototherapy directs the energy from the wavelength properties of light to create Photobiomodulation / stimulation within cells, tissues and organs.
“NASA SLEDs stimulate the basic energy processes in the mitochondria (energy-factory compartments) of each cell, particularly when near-infrared light is used to activate the wavelength sensitive constituents inside (chromophores, cytochrome systems). Optimal light wavelengths [researched in prior studies of laser and SLED light (Karu, 1989; Lubart, 1992; Beauvoit, 1994, 1995; Whelan, 1999, 2000, 2001; Sommer 2001)] to speed wound healing include 680nm, 730nm, and 880 nm. These wavelengths can be produced accurately by NASA SLEDs, which have a bandwidth of 25nm. The depth of near-infrared light penetration into human tissue has been measured spectroscopically (Chance, 1988; Beauviot, 1994, 1995). Spectra taken from the wrist flexor muscles in the forearm and muscles in the calf of the leg demonstrate that most of the photons at wavelengths between 630-800 nm travel approximately 23 cm through the skin surface (light input) and muscle, exiting at the photon detector” (Whelan et al 2001) .
