One example is sunlight being absorbed by the surface of the earth. However, the reflection of light from the surface tends to produce light of longer wavelength called infrared (IR) radiation. IR radiation is also radiated from a hot surface like a hot piece of metal.
For a black body, the heat current radiated off it, may be described as:
- is the area of the body
- is it's emissivity
- is the Stefan-Boltzmann constant
- is the temperature of the body