History of Planck's equation(s)

[tade]

I've only got a layman understanding of this.

Why did Planck find quantization necessary and how did he come up with the equation E = hf?

 

[Passionflower]

I've only got a layman understanding of this.

Why did Planck find quantization necessary and how did he come up with the equation E = hf?

The internet is your friend:
http://en.wikipedia.org/wiki/Planck's_law

 

[tade]

The internet is your friend:
http://en.wikipedia.org/wiki/Planck's_law

But it doesn't explain it very well.

 

[Passionflower]

But it doesn't explain it very well.

We seem to disagree on that, I think the article is excellent.

 

[DiracPool]

I've only got a layman understanding of this.

Why did Planck find quantization necessary and how did he come up with the equation E = hf?

Planck was trying to explain blackbody radiation, or basically the spectrum of energy that came out of an idealized heat/radiating emitting source. He found that as the energy put into the black body was raised, the peak frequency of radiation emitted increased up to a point in the ultraviolet spectrum, and then the peak frequency dropped suddenly. This was not expected in the models that existed at the time, and was hence dubbed "the ultraviolet catastrophe."

Planck found that the only way to deal with this catastrophe was to look at the energies emitted from the blackbody as coming in discrete packets, or quanta. The figure h, roughly 10^-34, multiplied by the frequency of a given wavelength of light, defined the energy, or the action, of that quanta.

In any case, that's the short and sweet of it, all from memory, so I hope I got it right. I think the real question you may be getting at is where did this cool h constant come from. The answer is nowhere special, it was found simply by experiment and not predicted by some grand theory of Planck's.

 

[tade]

I think the real question you may be getting at is where did this cool h constant come from.

Sorry, that wasn't my question.

Planck found that the only way to deal with this catastrophe was to look at the energies emitted from the blackbody as coming in discrete packets, or quanta.

That's my question. Why are quanta necessary? And E = hf

 

[DennisN]

That's my question. Why are quanta necessary? And E = hf

Blackbody radiation, as mentioned above, is the start of this thing. Planck's law is accurate, Rayleigh–Jeans law is not.

Furthermore, the photoelectric effect shines more light on the quantization of light (several puns intended ).

 

[tade]

Blackbody radiation, as mentioned above, is the start of this thing. Planck's law is accurate, Rayleigh–Jeans law is not.

Furthermore, the photoelectric effect shines more light on the quantization of light (several puns intended ).

Yeah, the photoelectric effect does explain it nicely.

But I want to know how Planck manged to come up with it by studying.. ovens. (Didn't he?)

 

[DiracPool]

That's my question. Why are quanta necessary? And E = hf

The long answer is given in the link Passionflower gave you, the short answer is that it has to do with the thermodynamics of the blackbody radiator. The energy of the radiating body is yielded through transitions of electrons in orbitals in the blackbodies atoms. These transitions occur in discrete jumps, which are parameterized by Plancks constant. That parameterization yields discrete energy units, or quanta, which manifest as emitted photons of discrete energy given by E=hf.

 

[vanhees71]

The photoelectric effect does not shed light on the quantization of light but on the quantization of the absorption of electromagnetic field energy due to the quantum nature of electrons. You get the photo effect from first-order time-dependent perturbation theory, where you treat the interaction of a qunatized bound electron with a classical electromagnetic plane wave as the perturbation.

 

[tade]

The photoelectric effect does not shed light on the quantization of light but on the quantization of the absorption of electromagnetic field energy due to the quantum nature of electrons. You get the photo effect from first-order time-dependent perturbation theory, where you treat the interaction of a qunatized bound electron with a classical electromagnetic plane wave as the perturbation.

But presumably both electrons and photons must have a quantum nature.

What is perturbation exactly?

 

[tade]

The long answer is given in the link Passionflower gave you, the short answer is that it has to do with the thermodynamics of the blackbody radiator. The energy of the radiating body is yielded through transitions of electrons in orbitals in the blackbodies atoms. These transitions occur in discrete jumps, which are parameterized by Plancks constant. That parameterization yields discrete energy units, or quanta, which manifest as emitted photons of discrete energy given by E=hf.

Guess I'll have to do it the long way.

 

[cabrera]

Plank didn't know anything about quantum nature of electron? Were photon known on that time.

 

[tade]

Plank didn't know anything about quantum nature of electron? Were photon known on that time.

??..

 

[capcom1983]

plancks equation is also ahead of its time it only really made sense after einstiens theory of relativity. He was try to solve the ultraviolet catastrophe because high frequencies need a high quanta of energy.

 

[capcom1983]

http://m.youtube.com/#/watch?v=i1TVZIBj7UA here's a nice video about Planck

 

[tade]

http://m.youtube.com/#/watch?v=i1TVZIBj7UA here's a nice video about Planck

thanks mate