Final answer:
Leaves appear green because chlorophyll, the pigment in leaves that conducts photosynthesis, absorbs blue and red wavelengths of light but reflects green light. The reflected green light is what gives leaves their characteristic color.
Step-by-step explanation:
The reason why plant leaves appear green is due to the pigment chlorophyll present in the leaves. Chlorophyll molecules are located in the thylakoid membranes inside chloroplasts, which are the organelles responsible for photosynthesis. Chlorophyll absorbs most of the wavelengths in the visible light spectrum, particularly the blue and red wavelengths, but it does not absorb green light effectively. Instead, it reflects and transmits the green wavelengths, which is why leaves appear green to our eyes.
The best way of explaining why the leaves on a given tree are green is: The molecules in the leaves absorb all visible light but strongly reflect green light. This phenomenon is supported by the absorption spectra of chlorophyll, which show distinct peaks where blue and red light are absorbed, but not for green light. Therefore, since green is the color that is least absorbed and mostly reflected by chlorophyll, it is the color that we see.