Doubt regarding Planck's Quantum Theory

In summary: If you want to know about light specifically and what causes light to act like a particle or a wave, you should read about duality of light. Light is a result of oscillating electric and magnetic fields perpendicular to each other. As Sir Tim has mentioned that frequency determines the energy of light, it is valid for all EMRs. But there is a relationship between frequency and wavelength of light also. The energy of a light wave depends on its frequency, but the frequency cannot be defined without wavelength. So, frequency and wavelength are also related. The duality of light is a very interesting fact. It states that light can behave both as a particle and as a wave depending on the situation. This is a very important concept in quantum mechanics and
  • #1
Sopandev
4
0
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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  • #2
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:​
 
  • #3
It travels as waves, but arrives as particles.
Is this applicable for all kinds of electromagnetic radiations?
 
  • #4


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?
 
  • #5
Sopandev said:
My question is, frequency of WHAT?
Thanks

It's the frequency of the oscillating atoms in the light emitter which emit photons.
 
  • #6
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.
 
  • #7


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...
 
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  • #8
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.
 
  • #9
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 frequecy.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
 

1. What is Planck's Quantum Theory?

Planck's Quantum Theory is a fundamental theory in physics that explains the behavior of particles at the atomic and subatomic level. It states that energy is not continuous, but rather it comes in small, discrete packets called "quanta."

2. How does Planck's Quantum Theory relate to classical physics?

Planck's Quantum Theory is a departure from classical physics, which assumes that energy is continuous and can take on any value. In contrast, Planck's theory proposes that energy is quantized, meaning it can only exist in specific, discrete amounts.

3. What is the uncertainty principle in relation to Planck's Quantum Theory?

The uncertainty principle is a fundamental principle of quantum mechanics that states that it is impossible to know the exact position and momentum of a particle at the same time. This is a direct consequence of Planck's Quantum Theory, as it introduces a fundamental uncertainty at the subatomic level.

4. What evidence supports Planck's Quantum Theory?

There is a wealth of experimental evidence that supports Planck's Quantum Theory, including the photoelectric effect, where light behaves as both a wave and a particle, and the double-slit experiment, where particles exhibit wave-like behavior. Additionally, modern technologies, such as transistors and lasers, would not function without the principles of quantum mechanics.

5. Are there any limitations to Planck's Quantum Theory?

While Planck's Quantum Theory has been incredibly successful in explaining the behavior of particles at the atomic and subatomic level, it is not compatible with the principles of general relativity, which govern the behavior of objects on a larger scale. This has led scientists to search for a unified theory that can reconcile these two branches of physics.

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