Doubt regarding Planck's Quantum Theory

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Discussion Overview

The discussion revolves around Planck's quantum theory, specifically addressing the nature of light and the relationship between its particle and wave characteristics. Participants explore concepts related to energy quantization, frequency, and the circumstances under which light exhibits particle-like behavior.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the meaning of frequency in the context of Planck's theory, suggesting that frequency may only apply when light is considered to have a wave nature.
  • Another participant clarifies that energy is propagated as waves but emitted or absorbed as particles, indicating a dual nature of light.
  • A participant seeks to understand the specific conditions under which light demonstrates its particle-like behavior.
  • There is a discussion about the relationship between the frequency of oscillating atoms in a light emitter and the emission of photons, with one participant expressing uncertainty about how these quantities are related.
  • Participants mention the double-slit experiment as an example where both particle and wave characteristics of light can be observed.
  • Some participants assert that all electromagnetic radiation exhibits similar properties, differing only in frequency.
  • One participant emphasizes the mechanical aspect of the radiant body and its thermal energy in relation to photon emission.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between frequency and the nature of light, with some asserting that light behaves as both a wave and a particle under different circumstances. The discussion remains unresolved regarding the specifics of these relationships and the conditions that compel light to exhibit its particle-like characteristics.

Contextual Notes

Participants reference concepts such as emission spectra and the mechanical properties of light-emitting bodies, but the discussion does not resolve the assumptions or dependencies underlying these ideas.

Sopandev
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Hello

We all see this statement everywhere : "Planck's quantum theory states that the radiant energy emitted or absorbed by a body is in the form of discreet packets of energy called Quanta, and the energy of the quantum depends on the frequency by the formula E = hv"

Now, my question is, that when Planck quotes that energy propagates in the form of quanta, he, according to me, means that Light has a particle nature. And then everywhere i see in the next line that energy of the quantum depends upon frequency.

My question is, frequency of WHAT?

Can't frequency only be defined when light has a wave nature?

Kindly clarify.
Thanks
 
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Welcome to PF!

Hello Sopandev! Welcome to PF! :smile:
Sopandev said:
"Planck's quantum theory states that the radiant energy emitted or absorbed by a body is in the form of discreet packets of energy called Quanta, and the energy of the quantum depends on the frequency by the formula E = hv"

Now, my question is, that when Planck quotes that energy propagates in the form of quanta, …

No, your quotation says that energy is propagated as waves (with a frequency), but is emitted or absorbed by a body as particles (quanta).

It travels as waves, but arrives as particles. :wink:​
 
It travels as waves, but arrives as particles.
Is this applicable for all kinds of electromagnetic radiations?
 


tiny-tim said:
It travels as waves, but arrives as particles. :wink:

Hey Tim

Thanks for that. Clears basic things up.

So exactly when in general does light show this particle-like behavior?
I mean, what circumstances compel light to show it's particle-like characteristics?
 
Sopandev said:
My question is, frequency of WHAT?
Thanks

It's the frequency of the oscillating atoms in the light emitter which emit photons.
 
Abdul Quadeer said:
It's the frequency of the oscillating atoms in the light emitter which emit photons.

Well?
How can the two quantities be related?

The frequency of the oscillating atoms in the light emitter(the radiant body) would be a quantity that would relate more with the mechanical aspect of the body, that could be the thermal energy possessed by the body. Oscillating atoms are actually the reason why the body mechanically exists, or has some form of mechanical energy.

On the other hand, the reason why photons are emitted from a body is an entirely different phenomenon. If we assume a body which emits light, it must be due to the existence of an emission spectrum unique to the body. This emission spectrum is caused due to the constituent atoms returning from a higher energy state to a lower energy state.

Please elaborate as to how the two are related.

Thanks.
 


So exactly when in general does light show this particle-like behavior?

In the double slit experiment one can see both the particle and wave nature of an electromagnetic wave...Read this... http://en.wikipedia.org/wiki/Double-slit_experiment
and Watch this...
 
Last edited by a moderator:
Welcome to PF!

Sopandev said:
So exactly when in general does light show this particle-like behavior?
I mean, what circumstances compel light to show it's particle-like characteristics?
gennarakis said:
So exactly when in general does light show this particle-like behavior?

In the double slit experiment one can see both the particle and wave nature of an electromagnetic wave...

Hi gennarakis! Welcome to PF! Hey Sopandev! :smile:

That's difficult to answer.

When we measure light (its frequency, its polarisation etc), it's a particle.

When we only interact with light without measuring anything about it (for example, when we divert it through a mirror), it's a wave.
 
My question remains unanswered. Is this applicable for all kinds of electromagnetic radiations.
 
  • #10
Sankalp for you the answer is YES. Sopandev basically Sir Planck refer to the pulse frequency.For clearing your doubt you have to dig deep yourself find an interpretation and compare with the older ones and then discuss it. I think it would be more helpful.
 
  • #11
Hi Sankalp Sethi! :smile:
Sankalp Sethi said:
My question remains unanswered. Is this applicable for all kinds of electromagnetic radiations.

There is only one kind of electromagnetic radiation (so yes) … the only difference between different radiations is the frequency. :wink:
 
  • #12
Sir Tim has written a true thing, All EMRs are a result of oscillating magnetic and electric fields.This is the the basic of EMR theory
 

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