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Dear Dr. Radiation,
I just went through your website descriptions of radiation physics. In general, it looks good, but a few things can use some clean up.
1. IR Equations: (I use Hudson's book Infrared System Engineering)
Planck's Law - OK (I use a simpler version, but this is OK (you might mention, this eq. generates the blackbody curves)
2. Stephan-Boltzman Law -
a. spelling errors on line 3
b. You should state that this gives the total energy emitted, but as the temperature rises, more of the energy is emitted at shorter wavelengths as given by Wein's Displacement Law and shown by the Planck blackbody curves. Thus, if you double the absolute temperature, you get 2 to the 4th or 16 times the TOTAL energy out, but more of this energy is output at shorter wavelengths and may not be felt as heat. (We normally consider the 8 to 12 micron region as thermal infrared).
3. Wein's Displacement Law - OK
Note: Our sun's energy at T=6000 K peaks at 0.5 µ (where our eye response also peaks). If our sun were cooler at 3000 K, its radiation would peak at 1.0 µ. (Our eyes, from evolution, would then peak at 1.0 µ, in the near infrared, but don't say this or you may catch Hell from some Born Again Creationist Christians who might be building Rumfords.)
4. Kirchhoff's Law : (Note spelling of Kirchhoff)
emissivity = absorbtance at any given wavelength and temperature
Thus "a good absorber is a good emitter" (which has to be true for the object to stay at the same temperature)
This can be expanded into the "common sense" equation I gave you that the total incident energy must equal the sum of the absorbed, reflected, and transmitted energy.
5. Absolute Zero in K=C+273.16
Absolute Zero in°Rankin=F+459.69
(Note: There is a new energy source being researched that gets its energy from the non zero momentum of atoms even at absolute zero - See Aviation Week article recently)
6. Greenhouse
Good quality quartz glass can transmit out to about 2 microns. 0.5 µ is blue light.
Objects at room temperature of about 80 °F (we call 300 K radiation) emit radiation which peaks at about 9.6 µ, which glass does not transmit. Thus the emitted energy from the inside objects in a greenhouse does not get out.
7. Glass doors.
Glass doors will not transmit the THERMAL infrared wavelengths from 8 to 12 µ, although they may transmit the short wavelengths around 1 µ, which we do not feel as heat. The glass will heat up, however, due to its absorptance and then will radiate out with an equal emissivity and at wavelengths determined by its temperature and Planck's Law.
Hope this is of some help.
If you want to chat about these items or some others, give me a call.
Regards to all,
Kimo
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