electricpete
Electrical
- May 4, 2001
- 16,774
Since I now work with infrared and Planck's formula for spectral distribution of blackbody energy or energy emitted from a cavity seems central to the subject, I googled on the subject of derivation of Planck's formula. I quickly came to the conclusion that the math involves is way above my head. But I saw a what seems to be a fascinating qualitative and historical discussions.
Raleigh Jeans had a formula based on classical electromagnetics.
RJ's formula worked well to predict observed behavior for high wavelengths but not short wavelengths... hence the ultraviolet catastrophe.
Plack stepped into the picture and used a model where only quantized energy levels were allowed (corresponding to discrete number of wavelengths in a cavity????). He somehow fit a curve of observed blackbody radiation to determine his famous constant h... later used by Einstein in connection with photon energy quantization.
So far pretty interesting but some questions come to mind:
1 - Does the above description sound roughly correct?
2 - How did they measure energy at a given wavelength in 1900? What kind of instrument?
3- What is the basic mechanism by which thermal molecular movement causes em radiation? Is it similar to movement of charged particles causing X-ray emission?
4 - What does Stefan Boltman got to do with it?
I know these are broad questions. Just looking for some quick easy answers to some questions on my mind if anyone has any thoughts.
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Raleigh Jeans had a formula based on classical electromagnetics.
RJ's formula worked well to predict observed behavior for high wavelengths but not short wavelengths... hence the ultraviolet catastrophe.
Plack stepped into the picture and used a model where only quantized energy levels were allowed (corresponding to discrete number of wavelengths in a cavity????). He somehow fit a curve of observed blackbody radiation to determine his famous constant h... later used by Einstein in connection with photon energy quantization.
So far pretty interesting but some questions come to mind:
1 - Does the above description sound roughly correct?
2 - How did they measure energy at a given wavelength in 1900? What kind of instrument?
3- What is the basic mechanism by which thermal molecular movement causes em radiation? Is it similar to movement of charged particles causing X-ray emission?
4 - What does Stefan Boltman got to do with it?
I know these are broad questions. Just looking for some quick easy answers to some questions on my mind if anyone has any thoughts.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.