The purpose of Plank's constant

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Discussion Overview

The discussion revolves around the purpose and meaning of Planck's constant, exploring its significance in quantum mechanics and its historical context. Participants seek clarification on its role in linking energy and frequency in blackbody radiation and its applications in various physical theories.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants inquire about the meaning of Planck's constant and its relevance to quantum mechanics, suggesting it relates to the size of phenomena at the quantum level.
  • One participant explains that Planck's constant (h) originally linked the energy of quanta of thermal radiation to their frequency, expressed as E=hν.
  • Another participant notes that the reduced Planck constant (ħ) is often used in place of h, particularly in discussions of angular momentum in quantum mechanics.
  • There is mention of the use of ħ in quantum field theory (QFT) where it is set to 1, indicating its role in the formulation of action in that context.
  • One participant requests a simpler explanation of the relationship between energy and frequency as described by Planck's constant.
  • A further explanation is provided, stating that Planck derived a dimensional constant to ensure the equation relating average energy and frequency was dimensionally correct.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding Planck's constant, with some seeking clarification while others provide technical details. No consensus is reached on a simplified explanation, and the discussion remains exploratory.

Contextual Notes

Some participants express uncertainty about the implications of Planck's constant in different theories and its historical development, indicating a need for further clarification on its applications and significance.

Gamish
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What is the purpose or meaning of Plank's constant? I keep on hearing about it, but I never learned what it is. Maybe it has to do with the size of everything on the quantum level. :rolleyes:

Thanks in advance
 
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Gamish said:
What is the purpose or meaning of Plank's constant? I keep on hearing about it, but I never learned what it is. Maybe it has to do with the size of everything on the quantum level. :rolleyes:

Thanks in advance

Though the original number was [itex]h[/itex] and it was called "Planck's constant",phyisicists did't like that number,so,instead they used the so-called:"reduced Planck constant",which is [itex]\frac{h}{2\pi}[/itex],which is more commonly seen and named:[itex]\hbar[/itex],i.e.HBAR.
In the original theory of Max Planck,it was a constant linking the energy of the quanta of (blackbody/thermal) radiation and its frequancy:
[tex]E=h\nu[/tex].
In the theory of Bohr,[itex]\hbar[/itex] it was regarded as the 'quanta for the angular momentum' of the electron orbiting the nucleus.From there on,in physics,[itex]\hbar[/itex] took the place of [itex]h[/itex].
In QM is is still regrarded as a 'quanta of angular momentum',this time on the (preferrentially chosen) Oz/Ox_{3} axis.
In QFT,though it's formulated in a system of units in which [itex]\hbar=1[/itex],[itex]c=1[/itex],it has the meaning of 'quanta of (lagrangian/hamiltonian) action'.


Daniel.
 
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dextercioby said:
In the original theory of Max Planck,it was a constant linking the energy of the quanta of (blackbody/thermal) radiation and its frequancy:

Can you please explaine what this means, in lamem terms
:rolleyes:
 
Gamish said:
Can you please explaine what this means, in lamem terms
:rolleyes:

Planck was computing the average energy per vibration mode for an isotropic stationary electromagnetic radiation and he came to an expression in which,in the LHS,it was average energy (measured in Joules) and in the RHS it was some adimensional constant (1 over some exponential) multiplied with frequency (of the radiation).So he invented a dimensional constant (known later as Planck's constant "h") to set the equation dimensionally correct.


Daniel.
 

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