Introduction to Blackbody Radiation

What is a Blackbody?

A blackbody is a theoretical object that absorbs 100% radiation. For example, carbon in graphite form absorbs all but about 3% of incoming radiation, making it a close approximation to a blackbody.

At a particular temperature, the black body would emit the maximum amount of energy possible for that temperature. This value is known as blackbody radiation.

Key Characteristics

  • Maximum wavelength emitted by a black body radiator is infinite
  • Blackbody emits a definite amount of energy at each wavelength for a particular temperature

Black Body Radiation Curves

Single Temperature Analysis (5800K)

Black Body Radiation Plot

Fig 1. Black Body Radiation Plot

The radiation curve touches the x-axis at infinite wavelength, demonstrating that blackbody radiates energy at every wavelength. At 5800K, the peak wavelength (wavelength that emits most energy) is about 5 × 10-7 m.

Temperature Variation Analysis

Black Body Radiation Curves at Various Temperatures

Fig 2. Black Body Radiation Curves at Various Temperatures

Temperature Effects on Radiation

Key Observations:

  • As temperature increases, the peak wavelength emitted by the blackbody decreases
  • Higher temperatures result in greater total energy emission, evidenced by increased area under the curve