Hi. I know this is a pretty basic principle, however I'm fairly new to the subject and was wondering if anyone is able to give a brief 'layman'
explaination of why, as Planck's law states, at lower wavelengths the blackbody radiation falls to zero rather than continuing to climb as stated in
the Rayleigh-Jeans law.
I have read a number of articles but none yet seem to have a basic enough explaination to allow me to 'picture' the principles involved.
Anyone that can help me with this would have my eternal gratitude!!
Thanks. 12AX7 - 27-6-2009 at 03:05
Because Rayleigh-Jeans "law" isn't real. Planck's law is physically significant.
The most blatantly obvious disproof is to observe how we aren't swimming in a dense sea of high energy gamma radiation.
"Most neutrinos passing through the Earth emanate from the Sun, and more than 50 trillion solar electron neutrinos pass through the human body every
second"
Ozone - 27-6-2009 at 08:10
Lookup "ultraviolet catastrophe" on wiki and start chasing paper there. I have always thought that "ultraviolet catastrophe" would be a great name for
a band.
Cheers,
O3
@12AX7:
Davies' Phosgene
rocks the world
Rock on,
O3
[Edited on 28-6-2009 by Ozone]12AX7 - 27-6-2009 at 18:00
wondering if anyone is able to give a brief 'layman' explaination of why, as Planck's law states, at lower wavelengths the blackbody radiation falls
to zero rather than continuing to climb as stated in the Rayleigh-Jeans law.
At low wavelengths, the energy in a single photon is large, and this is too big for the amount of energy available implied by the temperature, and so
these states do not happen.
Without the quantization, you could have fractional amounts of this energy at that wavelength, and so you can happily have some spectrum at lower and
lower wavelengths, contrary to observation. JohnWW - 28-6-2009 at 15:01
According to the Stefan-Boltzmann equation, which can be derived from the Planck equation (according to which the wavelength of peak radiative
emission of a body decreases with temperature), the total radiation from a body at all wavelengths is proportional to the 4th power of absolute
temperature. This means that both shorter (and hence more energetic, E = hf = hc/L) wavelengths, and increased total emission, are associated with
increasing temperatures.
.