Why are Leaves Green?
Sunlight appears to be white light but is in fact made up of seven different coloured lights!
You can see these colours when sunlight shines through a prism because prisms bend light, separating all the colours usually hiding inside the white sunlight.
Understanding why leaves are green requires us to understand a little about Light and Pigments, explained below:
- While sunlight appears white to our eyes, it is made up of a spectrum of seven colours (or wavelengths). These colours are red, orange, yellow, green, blue, indigo, and violet.
- Pigments are molecules which give things colour, from our skin colour to the colour of grass.
- If a pigment is red, it means that it absorbs all other colours in the spectrum except red, which reflects back to our eyes. Each colour in the spectrum provides a different form of energy.
- A green leaf has green pigment used in a process called Photosynthesis, a process turning light from the sun, together with carbon dioxide and water the leaf has absorbed, into its food (sugars).
- Photosynthesis requires a green pigment called Chlorophyll. Chlorophyll absorbs all six other colours and reflects green.
A prism refracts (bends) light through the angles and panes of its surfaces. This splits sunlight (white light) into its seven individual colour wavelengths, which our eyes alone are unable to see.