Light s the form of energy and it travels as a stream of tiny particles. Quantum represents the energy contained in an individual proton. Light represents only one part of electromagnetic radiation. And cosmic rays, X-rays, UV rays, infra-red radiation and radio waves. A visible right has seven separated groups of more or less complete absorption. In a spectrum of sunlight, bands of blending colors are seen dark red at one end running through red orange yellow green blue indigo violet portion of spectrum are about 400 millimicrons in length and at other end of spectrum-the red portion-are much longer about 730 millimicrons. In other words, visible light lies between wavelengths of ultra-violet and infra-red. The most efficient wavelengths of light effective in photosynthesis are those or red light. Green light is least effective and has inhibitory effect. However art of blue and red wavelengths, blue light carry more energy.
Absorption and Acton spectra:
The curve representing the light absorbed at each wavelength by pigment is called absorption spectrum. Curve showing rate of photosynthesis at different wavelengths of light is called action spectrum. Absorption spectrum is studied with the help of spectrophotometer. The absorption spectrum of chlorophyll a and chlorophyll b indicate that these pigments mainly absorb blue and red lights. Action spectrum shows that maximum photosynthesis takes place in blue and red regions of spectrum.
In this case actual rate of photosynthesis in terms of oxygen evolution or carbon dioxide utilization is measured as a function of wavelength. Both chlorophyll a and b show an absorption maximum in blue and red regions.
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