- When sunlight strikes an opaque object or material, it can be reflected or absorbed.
- If the light is reflected it bounces off at the same wavelength.
- If the light is absorbed, its energy is transferred to electrons which re-emit the energy as heat.
- Of the light that reaches Earth’s surface from the Sun:
- 54% is already heat (infrared wavelengths of light) before it reaches the earth’s surface.
- 45% is visible light.
- 1% is shorter wavelengths (ultraviolet).
- Absorption of a particular wavelength of light into a material takes place when the frequency of the wave matches the frequency of electrons within it. As electrons within atoms absorb energy and heat up they vibrate more vigorously causing the atoms to collide with one another.
- Because the electrons in different atoms have different frequencies they selectively absorb different frequencies of visible light.