Absorption Spectrum Chlorophyll

Edexcel A-level BiologyPhotosynthesisLesson 5 of 20

An absorption spectrum is a graph showing how much light a pigment absorbs at each wavelength. It is measured by passing light of different wavelengths through a pigment extract in a spectrophotometer (or a colorimeter with filters).

Key features:
• Chlorophyll a has two main peaks, in the blue (about 430 nm) and red (about 660 nm) parts of the spectrum.
• Chlorophyll b has peaks at slightly different wavelengths, closer together, extending absorption in the blue and orange-red.
• Carotenoids absorb mainly blue-violet light, from about 400 to 500 nm.
• Very little light is absorbed between about 500 and 560 nm, the green part of the spectrum.

More in Photosynthesis

• Autotrophs and Heterotrophs
• The Process of Photosynthesis
• Chloroplasts
• Chlorophyll
• Chromatography
• Photosystems
• The Light-Dependent Reactions
• Cyclic Photophosphorylation

All 20 lessons in Photosynthesis · All Edexcel A-level Biology topics