File:Stealth-grow-LED-full-spectum-graph.jpg

PAR, MH and LED spectra compared.

Source: http://www.stealthgrow.com/facts.htm

Light Spectrum and Absorption

200-280nm UVC ultraviolet range, which is highly toxic and extremely harmful to plants. 280-315nm Includes harmful UVB ultraviolet light, which causes plant colors to fade. 315-380nm Range of UVA ultraviolet light that is neither harmful nor beneficial to plant growth. 380-400nm Start of visible light spectrum. Process of chlorophyll absorption begins. UV protected plastics ideally block out any light below this range. 400-520nm This range includes violet, blue, and green bands. Peak absorption by chlorophyll occurs, and a strong influence on photosynthesis (promotes vegetative growth.) 520-610nm This range includes the green, yellow, and orange bands and has less absorption by pigments. 610-720nm This is the red band. Large amounts of absorption by chlorophyll occur, and most significant influence on photosynthesis (promotes budding and flowering.) 720-1000nm There is little absorption by chlorophyll here. Flowering and germination is influenced. At the high end of the band is infrared, which is heat. 1000+ Totally infrared range. All energy absorbed at this point is converted to heat.