Thermal Radiation Curves
If you graph the intensity (that is, the amount) of thermal radiation given
off by a star as a function of wavelength, you will get a graph like this:
These curves are called "thermal radiation curves." The red curve shows thermal
radiation as a function of wavelength for a star at 3730 C (6750 F). The blue
curve shows a star at 5730 C (10,350 F) - a little hotter than the sun. The green
curve shows a star at 7730 C (14,400 F).
The curves show that hotter stars give off more thermal radiation, just as the hot plate
glowed brighter as you heated it up. The curves also show that the peak wavelength of the
thermal radiation (the thin black line) moves to shorter wavelengths as the
temperature increases. The 3730 C star has a peak wavelength near the border between
red and infrared light. The 5730 C star has a peak wavelength in the blue
wavelength of light. The 7730 C star has a peak wavelength in ultraviolet light.
Explore 3. This interactive Java applet will
help you learn how thermal radiation curves change with temperature. Click on the link
to open a new window, then read the instructions. Try several different temperatures
and peak wavelengths. Can you find a mathematical relationship between temperature
and peak wavelength? |
| 
