6.2  Light Reactions

Solar energy can be described in terms of its wavelength and energy content.

While there are several forms of solar, or radiant energy, that strike the Earth's atmosphere, visible light is the form of energy that our eyes can use to see. 


Colors of sunlight

Photosynthetic Pigments

The two primary pigments used during photosynthesis are chlorophylls and carotenoids.

Chlorophylls absorb violet, red, and blue wavelengths of visible light and reflect green light (this is why they look green to our eyes). 

Carotenoids absorb in the violet-blue-green range but reflect yellow-orange wavelengths (this is why they look yellow-orange to our eyes).


Leaf colors

The carotenoids and other pigments become visible in the autumn as the leaf dies and chlorophyll is degraded.

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Chlorophyll absorbs green light.



Extra Help


More about the light reactions