What is Blackbody Radiation?
Blackbody radiation is the thermal radiation emitted from, rather than reflected by, an object. Physically, blackbody radiation is always mixed with reflected radiation, because all real-world objects reflect some of the electromagnetic waves they receive. Nonetheless, a hypothetical black body would emit radiation dependent only on its temperature. Hot black bodies would emit substantially in the visible range of light and, therefore, would be visible to humans. Cool black bodies would emit mainly in the infrared range, making them invisible to the human eye.
