One can not understand black body radiation without first understanding the nature of so-called black body objects.
A black body object is one which all wavelengths of electromagnetic radiation are completely absorbed. Also, and really a result of this nature, black bodies are also perfect emitters of thermal radiation.
The specific radiation that is emitted is dependent on the temperature of the black body. For temperatures near "room temperature", the peak wavelength of emission lies in the infrared.
Since many household items are good approximations of black body objects, when heated these objects will then emit infrared radiation.
This is actually a problem in infrared astronomy because when infrared telescopes are operating their electronics heat up due to use. And due to their black body nature they would naturally then emit infrared radiation which would interfere with the detection of radiation from astronomical objects.
Researchers get around this problem by using liquid helium to continually keep the instruments cool, thereby reducing the self-detamination of any infrared signals.
Black Body Radiation and Wien's Law
When a black body is heated it will emitted radiation due to the thermal energy of the object. But it does not just emit a single wavelength, but rather a distribution of light that is peaked at a specific wavelength.
The peak wavelength can be determined using an expression known as Wien's Law.
Specifically, Wien's Law states that the peak wavelength can be determined by dividing a number known as Wien's displacement constant (approximately 2.9×10−3 K m) by the temperature of the black body (expressed in kelvin).
Examples of Black Bodies and Black Body Radiation
There is no such thing as a "perfect" black body, but many objects, such as the coils on your stove or even the human body, are good approximations.
One of the more obvious ones, particularly relating to astronomy, is our Sun. The surface of Sol is roughly 6,000 Kelvin (or degrees Celsius if you prefer; at these temperatures the difference is almost negligible).
The Earth is also considered to be a black body radiator, though it is certainly less than ideal.
