About Infrared Photography
The effect is named after the infrared photography pioneer Robert W. Wood. Attributes of infrared images include dark sky and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering, respectively, compared to visible light. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly. Infrared wavelengths also penetrate a few millimeters into skin and give a milky look to portraits, although eyes often look black.
Often in infrared a measure of light will be indicated of an image in nm (nanometer / nanometre), which photographically indicates filtered wavelength. The nanometre is commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light ranges from around 400 to 700 nm. Foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow, is an example of infrared light in respect to wavelength (nm) and reflectivity effect. Infrared photo filters range from 400nm to 1200nm, where the shorter spectrum will add more color tone than the longer monotone (red) wavelength.
*Thanks to Wikipedia for wording and most info , above.