Quantum Physics: Energy in Packets

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Discussion Overview

The discussion revolves around the nature of energy in quantum physics, specifically focusing on the concept of energy being absorbed in the form of quanta, such as photons. Participants explore whether absorbed energy remains as packets or is destroyed, the implications of absorption on the existence of photons, and the relationship between energy absorption and mass increase in sub-atomic particles.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose that when energy is absorbed, such as in the case of photons, the photons are "gone" or destroyed, while others argue that they are simply absorbed and thus still exist in a different form.
  • There is a question about whether the absorption of photons means they lose their existence, with some suggesting that the number of photons in the universe is not constant and that photons can be created through various processes.
  • Participants discuss the fixed amounts of energy in electromagnetic waves, represented by the equation E = hf, and how this relates to the absorption of photons by electrons.
  • Some participants challenge the terminology of "destroyed" versus "absorbed," with differing views on whether the photon ceases to exist or simply transforms into another form of energy.
  • A later reply introduces the idea of whether the absorption of a photon increases the mass of an electron, leading to further discussion on the implications of energy addition on mass in sub-atomic particles.

Areas of Agreement / Disagreement

Participants express differing views on whether absorbed photons are destroyed or simply transformed. There is no consensus on the terminology used to describe this process, and the discussion remains unresolved regarding the implications of photon absorption on existence and mass.

Contextual Notes

Some statements rely on specific interpretations of quantum field theory and non-relativistic quantum mechanics, which may not be universally accepted. The discussion also touches on the definitions of energy conservation and the nature of photons as fundamental particles.

vipulsilwal
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i have just started studying quantum physics, please clear this doubt

energy is in small packets called quanta. when a body absorbs heat(form of energy) these packets are absorbed. so after being absorbed are they destroyed (or disintegrated) or remain in form of packets.
i believe it should remain in form of packets.
please correct me, if i am wrong.
 
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When photons are absorbed, the results are more energetic electrons, atoms, or molecules, depending on the photon energy. The photons are gone.
 
'gone', does that means they are destroyed??
if that is the case, then for again making a photon(when body radiates energy) there should be some driving force or something that keeps that photon integrated(intact).
are there some constituents of photons too?
 
vipulsilwal said:
'gone', does that means they are destroyed??
if that is the case, then for again making a photon(when body radiates energy) there should be some driving force or something that keeps that photon integrated(intact).
are there some constituents of photons too?

"destroyed" is a misnomer, they are absorbed. An example - microwave oven. The energy is absorbed by the water and it gets hot.

Photons don't have constituents - they are fundamental particles of energy.
 
Last edited:
something which gets absorbed does it loses its existence?
if not, then number of photons in universe will always remain constant?
if no, how they are created?
 
vipulsilwal said:
something which gets absorbed does it loses its existence?
if not, then number of photons in universe will always remain constant?
if no, how they are created?

Absorption means going out of existence. No. of photons in universe is not constant. Photons are created whenever some process generates them. Examples: microwave oven, TV transmitter, flashlight, etc.
 
we don't know why you can only add or subtract energy from an electromagnetic wave in fixed amounts (quanta) but we know the amount in a packet is E = hf. So a photon is one packet and contains hf. So it's frequency dependent.
If the amount of energy in a photon is close to the amount of energy required to move a bound electron into a higher orbit it is absorbed.
At low frequencies the photon has small energy and may be absorbed into the quantised vibration of a molecule. This is infra red radiation causing the molecule to warm up. That is, vibrate faster.
 
mathman said:
"destroyed" is a misnomer, they are absorbed. An example - microwave oven. The energy is absorbed by the water and it gets hot.

Photons don't have constituents - they are fundamental particles of energy.

Is "destroyed" really a misnomer? When you say "absorbed" I think of a feynman diagrams with an electron and photon coming in and an electron going out. I say it is destroyed. The energy and other defining properties may be conserved but the photon doesn't exist anymore. This seems true from a QFT point of view and from a non-relativistic QM point of view where we quantize the electromagnetic field.
 
whynothis said:
Is "destroyed" really a misnomer? When you say "absorbed" I think of a feynman diagrams with an electron and photon coming in and an electron going out. I say it is destroyed. The energy and other defining properties may be conserved but the photon doesn't exist anymore. This seems true from a QFT point of view and from a non-relativistic QM point of view where we quantize the electromagnetic field.

I think it is simply a matter of definition. To my mind absorbed is better, since the energy goes into the energy of motion of the electron or something similar. Destroyed to me means it is no longer there at all.
 
  • #10
A photon is not a little ball bearing with energy. It's a quantum of energy. Energy can't be destroyed, but after a photon is absorbed it no longer exists. If absorbed by a bound electron the electron may, after a brief time delay, relax to the original state by emitting a photon. This is not the original photon because its direction of motion is likely to be random.
 
  • #11
I would like to extend the question. When a photon is absorbed by an electron, making the electron more energetic, does this increase the mass of the electron?

Curioso
 
  • #12
Yes.
What applies to matter in general does not always apply to sub-atomic particles. For matter any increase in temp, angular momentum, density, (that is, any energy addition) increases the mass. and thus the the gravitation.
 

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