Thermal Radiation

An object’s temperature is the measure of the speed at which the object’s particles move. To measure temperature, astronomers prefer the Kelvin temperature scale . This scale is much like Celsius, but 0 is Absolute Zero – scale starts at zero, 0K.Wien’s Law relates the color of an incandescent object to its temperature. The law states that wavelength of the brightest color is inversely proportional to the object’s temperature.

Image of Wien’s Law in an equation. The wavelength of the brightest color multiplied by one divided by t.

Where:

  • λmax is the wavelength of the brightest color
  • is the temperature

Stefan-Boltzmann Law states that the power, , emitted per unit of area of an object is proportional to the fourth power of its temperature, . Mathematically, this is:

Image of Stefan-Boltzmann Law in an equation. Power, P , emitted per unit of area of an object is proportional to the fourth power of its temperature, T

Where:

  • is the power
  • is the temperature