What exactly is the Ultraviolet Catastrophe?

JoshBuntu

I tried looking it up, but I just don't get it. Something about intensity going to infinite(?)

What exactly was the original theory and how does the "quantized" theory account for stuff?

I'm sorry if this is a dumb question :/

Naty1

The problem was that classical theory gave an infinite (silly) answer for black body radiation....quantum theory via Planck solved the riddle....

This is a good explanation...

http://en.wikipedia.org/wiki/Ultraviolet_catastrophe

vijayan_t

the intensity is decreasing for higher frequency. see this explanation
http://www.youtube.com/watch?v=4o9mCTXE-UQ

sophiecentaur

That bit involving lengths of string is a bit fanciful. How ever is it supposed to show the difference in powers? The rms power is the same for all frequencies of waves of similar shape and same amplitude. What has the length of a piece of string got to do with it? How does the string relate to photons?

Born2bwire

Are you talking about the wiki link? I don't see such contradictions in the very brief mention of harmonics on a string. They just used it as a brief analogy to help show that the density of states for a classical harmonic oscillator increases with the frequency.

sophiecentaur

Wow - I'm sorry. I was referring to (complaining about) the UTube clip in the other post. I just quoted the wrong post - durr.
In the UTube movie, they were showing a progressive wave with the string (referring to light ) and relating the length of the string that they unwound off some pins to the energy of the wave. That passage made no sense to me as the string was no more than a graph of displacement (possibly?) with distance. How does that relate to energy? It was so bad that I really couldn't go along with any more of it.
The Wiki link was fine btw.

Emilyjoint

In classical theory energy can be shared amongst waves of all frequencies. If a box contains electromagnetic waves there will be more waves in a range of frequencies at the high frequency end than at the lower frequency end and this suggests that more of the energy will be at the high frequency end (ultra violet is high frequency waves).
Plancks theory states that energy can only be emitted or absorbed in packets called photons. The energy of a photon is proportional to the frequency. ALSO the probability of getting a high energy photon (compared to the average energy) is lower. Just like the probability of finding a very high energy molecule in a gas at a certain temperature (average energy). This accounts for the shape of the black body spectrum just like the Boltzmann distribution accounts for speed distribution of molecules.

Born2bwire

Yeah, that was my guess but I wasn't willing to sit through an 8 minute video to find out.

sophiecentaur

Zero out of ten for production values and not much more for content, I think!