Remember - for thermal radiation - the frequency of light (the energy
of each
photon) is proportional to the temperature of the emitter:
Human body = 300 K Þ 10
microns, or 100,000 Å (infrared)
Sun, light bulb filament =
6000 K Þ 5000 Å (visible, yellow)
Hot star’s surface = 40,000
K Þ 750 Å (far ultraviolet)
Really hot plasma =
5,000,000 K Þ 6 Å (X-ray)
*don’t forget that thermal emitters give off photons with a range of wavelengths;
those listed above represent the peak of the distribution