History of Planck's equation(s)

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In summary: No, Planck wasn't the first to understand the quantum nature of electrons. He was simply the first to quantify it in a meaningful way.
  • #1
tade
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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?
 
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  • #2
tade said:
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
 
  • #3
  • #4
tade said:
But it doesn't explain it very well.
We seem to disagree on that, I think the article is excellent.
 
  • #5
tade said:
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.
 
  • #6
DiracPool said:
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.
DiracPool said:
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
 
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  • #8
DennisN said:
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 :smile:).

:smile: 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?)
 
  • #9
tade said:
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.
 
  • #10
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.
 
  • #11
vanhees71 said:
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?
 
  • #12
DiracPool said:
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. :redface:
 
  • #13
Plank didn't know anything about quantum nature of electron? Were photon known on that time.
 
  • #14
cabrera said:
Plank didn't know anything about quantum nature of electron? Were photon known on that time.

??..
 
  • #15
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.
 
  • #17

1. What is Planck's equation?

Planck's equation, also known as Planck's law, is a fundamental equation in physics that describes the relationship between the energy of a photon and its frequency. It was developed by German physicist Max Planck in 1900 and is a cornerstone of modern quantum mechanics.

2. What is the significance of Planck's equation?

Planck's equation revolutionized the field of physics by providing a theoretical foundation for understanding the behavior of light and other forms of electromagnetic radiation. It also marked the beginning of quantum theory, which has had a profound impact on our understanding of the universe.

3. How did Planck come up with his equation?

Planck's equation was developed as a result of his attempts to explain the behavior of blackbody radiation. He proposed that the energy of a photon is directly proportional to its frequency, with the proportionality constant being known as Planck's constant.

4. Are there any other versions of Planck's equation?

Yes, there are several versions of Planck's equation that have been developed over the years to describe different phenomena. Some of the most well-known versions include the Planck-Einstein relation, which relates the energy of a photon to its wavelength, and the Bose-Einstein distribution, which describes the distribution of particles in a quantum system.

5. How has Planck's equation been applied in other fields?

Planck's equation has had a wide range of applications in fields such as astrophysics, chemistry, and engineering. It has been used to study the properties of stars, develop new technologies such as lasers and solar cells, and even explain the behavior of particles in the early universe. Its impact on modern science cannot be overstated.

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