Solar energy capture for biosphere. Source of organic building blocks for biosphere. Supplied O 2 for aerobic respiration. Food source for all heterotrophs. Photochemistry is involved, but most of the reactions are not photochemical.
Visible light is small part of spectrum.
Has wave and particle properties. Energy of photons inversely related to wavelength. More photons in red and longer l than in blue. 7.3 Pigments like chlorophyll absorb specific wavelengths. . Blue and red wavelengths absorbed.