# Is there a limit to how much energy can be stored in a photon?

## Main Question or Discussion Point

hi all, I have a couple of questions.

is there a limit to how much energy can be stored in a photon?

And why does the spectrum only go to gamma rays?

And what is the higest observed energy and what made it ?

Thanx in advance

## Answers and Replies

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Khashishi
Science Advisor
There is no limit to how much energy there can be in a photon, unless you start getting into some speculative theories.

tom.stoer
Science Advisor
There is no upper limit. The energy E is simply E=hf, and the frequency f can be arbitrary high. The only question is whether the are processes via which high-energy photons a produced.

what would be above gamma rays? And how could these be produced.

and what is the higest frequency photon observed?

Bill_K
Science Advisor
and what is the higest frequency photon observed?
The highest measured energy is 16 TeV. At least, that's what it says here.

Nugatory
Mentor
The highest measured energy is 16 TeV. At least, that's what it says here.
That's 16 Joules as I read the wiki... an almost mind-boggling number, enough energy to be macroscopically observable.

the wiki article implies the existance of up to 10Eev

There is a limit to absorbed an energy into a photon. Some theories don't let us think that......... eg., Quantum Theory and basic principle laws of Quantum Mechanics, for that we have to do research on it.

can any known proces produce 100 Eev photons?

tom.stoer
Science Advisor
There is a limit to absorbed an energy into a photon. Some theories don't let us think that......... eg., Quantum Theory and basic principle laws of Quantum Mechanics, for that we have to do research on it.
If you don't know any such theory, what makes you believe that there is one?

I'm not sure that you can say a photon is anything besides energy. Is there a limit to the amount of energy stored in energy o_0 ???

Bill_K
Science Advisor
I'm not sure that you can say a photon is anything besides energy. Is there a limit to the amount of energy stored in energy o_0 ???
A photon is not just disembodied energy! It exists, with a full set of properties, on the same basis as all the other elementary particles. In addition to energy and momentum it carries one unit ħ of spin, has space parity -1, charge parity -1, and couples to a conserved quantity, namely the charge-current 4-vector.

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once again, can any KNOWN process generate hypotheticly, 100 Eev photons? If so please give me the name.

Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
There is not a limit.

Proof: Consider the following: suppose there were a maximum energy, E_max. You create a source of photons of energy E_max. Now you start walking towards it, blueshifting them. Now their energy is greater than E_max.

A photon is not just disembodied energy!
Hehe, I'm saying that it is disembodied because it has no dimensions in classical space. All of those quantum numbers are not what I would normally think of as a "body"... Perhaps you could think of all of those numbers as being vectors in Hilbert space. Then I guess you could say it's "embodied"!

tom.stoer
Science Advisor
once again, can any KNOWN process generate hypotheticly, 100 Eev photons? If so please give me the name.
You can annihilate an electron-positron pair with sufficiently high energy.
You can blue shift a photon (e.g. the cosmic background radiation) to arbitrary high energy by accelerating yourself.

is there a limit to how much energy can be stored in a photon?
As mentioned above the answer is no. Although saying that a photon stores energy seems like a quirky way to put it.

And why does the spectrum only go to gamma rays?
I would hazard go guess that the term gamma ray refers to any photon above a certain energy so that the photon energy levels to the right of all observed gamma rays corresponds also to gamma rays.

It's theoretically possible to move at any speed relative to a source of photons. As such you can move as close to the speed of light as you wish. The faster you go relative to the source of photons the higher the photons energy will be and as such there is no theoretical upper bound to the energy of gamma rays.

Borek
Mentor
Note that while there is no limit on the energy of a single photon, there is a limit on the energy of the photons coming to us from distant sources. If they have energy high enough they will interact with the background radiation, so they will be filtered out. Google for Greisen–Zatsepin–Kuzmin limit.

what hapens if photon a with 10Eev energy and photon b with same energy collide head on? And what if three with the same energy collide with equal angles away from each other?

tom.stoer
Science Advisor
what hapens if photon a with 10Eev energy and photon b with same energy collide head on?
In each collision a pair of charged particle/antiparticle is produced. Depending on the particle species further particle production will occure. If e.g. an electron-positron pair is created, nothing else happens. If a quark-antiquark pair is produced the will hadronize in two jets.

what hapens if photon a with 10Eev energy and photon b with same energy collide head on? And what if three with the same energy collide with equal angles away from each other?
There is something called photon-photon scattering. I believe that the scattering cross section is quite small though. So for the most part they don't interact. I don't know much about this process but you can learn more about it at http://www.nrcresearchpress.com/doi/pdf/10.1139/p11-144

why does that happen if i may ask. Why for example dont they superpose like a clasical transverse wave?

tom.stoer
Science Advisor
Why ... dont they superpose like a clasical transverse wave?
They do.

The two-photon state is (in the QFT-sense) the linear superposition of two one-photon states.

But due to the non-linearity encoded in the photon-fermion interaction term of the Hamiltonian (in Feynman diagram language the photon-fermion vertex), the S-matrix contains diffent channels

Besides the trivial (classical) non-interacting channel

$$|2\gamma\rangle \to |2\gamma\rangle$$

there are (infinitly many) interacting channels, e.g.

$$|2\gamma\rangle \to |e^+\,e^-\rangle$$

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the wiki article on two-photon physics doesnt contain much info, any good links?