Perfect Black Bodies (GCSE Physics)

Perfect Black Bodies

Infrared Radiation and Temperature

• Infrared radiation always occurs. No matter what the temperature of  an object is, it will always emit and absorb infrared radiation. All objects will obey this rule.
• Heat can increase infrared radiation. If the temperature of an object is increased, the the amount of infrared radiation it emits will also increase. More simply we can say that the hotter an object is, the more infrared radiation it will radiate.

A Perfect Black Body

For exams, you need to know the definition of a perfect black body:

A perfect black body is an object that absorbs all of the radiation incident on it.

Defining Black Body Radiation

• Black bodies cannot reflect or transmit. Black bodies cannot reflect or transmit the wavelengths of light. This means that black bodies will not appear transparent and they will not appear a certain colour. Instead, all of the wavelengths are absorbed, resulting in the object being a ‘black body’.
• Black bodies are good radiation emitters. Since a good absorber is also a good emitter, black bodies are very good at emitting radiation. In fact, black bodies are the best emitters compared to any other objects.