Describe the electromagnetic radiation emitted by an object due to its temperature.

• Matter will spontaneously convert some of its internal thermal energy into electromagnetic energy.
• A blackbody is an idealized model of matter that absorbs all radiation that falls on the body. If the body is in equilibrium at a constant temperature, then it must in turn emit energy.
• A blackbody will emit a continuous spectrum that only depends on the body’s temperature. The radiation emitted by a blackbody is often modeled by plotting intensity per unit wavelength as a function of wavelength.
• The distribution of the intensity of a blackbody’s spectrum as a function of temperature cannot be modeled using only classical physics concepts. A blackbody’s spectrum is described by Planck’s law, which assumes that the energy of light is quantized.
• The peak wavelength emitted by a blackbody (the wavelength at which the blackbody emits the greatest amount of radiation per unit wavelength) decreases with increasing temperature, as described by Wien’s law. Relevant equation:
• The rate at which energy is emitted (power) by a blackbody is proportional to the surface area of the body and to the temperature of the body raised to the fourth power, as described by the Stefan-Boltzmann law. Relevant equation:

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Simulation page: Blackbody Spectrum