Objects (Level 1)

Transilluminated Leaf
Leaves look the way they do because of the stuff they are made of. When leaves, like this one from a sugar maple, change in the fall we can see different stuff in them and the green is replaced by bright yellows, oranges, and reds.

Why are Leaves Green?

Since color is a perception, leaves are green simply because that's the way we see them!

But why do we see them that way? That's because of the stuff leaves are made of and how it plays with the light from the sun. One sort of stuff in the leaves is called chlorophyll. Chlorophyll is the main part of the leaf that makes them so good for nature. The chlorophyll takes carbon dioxide (CO2) from the air and uses water and energy from sunlight to create sugar. That sugar is food for the tree and for animals (like us) that eat the leaves or make yummy things like maple syrup from the tree sap.

The light energy that the chlorophyll uses is mainly the types that would look red or blue to us. That leaves the green energy to bounce off (or pass through) the leaves and reach our eyes. And when that light reaches our eyes we see the leaves as green.

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Ever wonder ... Why do leaves change color in the autumn?


Updated: Apr. 11, 2011