Prime objective of this lecture is to present on Absorption of Light by Chlorophyll. here briefly present on measuring light absorption: A spectrometer is used to measure the amount of absorption at each wavelength. An action spectrum shows the rate of photosynthesis at different light intensities. Chlorophyll A and B absorb light mostly in the red and blue regions of the spectrum. Carotene and xanthophyll absorb light from other regions and pass the energy to chlorophyll.