
#1
Dec1913, 11:05 AM

P: 35

Hello
I am a physics student at the university of Athens (1st year) . Recently i have been studying special relativity by myself and i have question that i cant understand by myself When we speak about photons and their energy we use this formula : E=hf where h : planks constant and f:frequency my question : How can we speak about the energy of photons and use frequenscy .. how can a photon have its own frequency ? and something else . Can an electron ( and in general every particle) be considered as a wave also ? (like the photons) 



#2
Dec1913, 11:28 AM

Sci Advisor
Thanks
P: 2,967





#3
Dec1913, 11:34 AM

P: 35

Understood and thank you ...
Actually i am taking physics courses via the internet and one of the lessons i am attending is called " introduction to relativity , nuclear physics and cosmology" so i believe i will have no problems .. 



#4
Dec1913, 11:55 AM

P: 5,634

question about photons
If your search for anything like 'photon energy' in these foums you'll find loads of prior discussions.
Briefly, in the standard model of particle physics relativistic quantum theories describe 'particles' as probabilistic wave functions, not like 'little balls'. When we detect such phenomena we observe them as point particles and physical action at small scales takes place in discrete steps as in multiples of 'h'. What they 'really are' between observations is less clear and you can find discussions in these forums... The particular quantum theory for light and matter is QED. Roughly, you can think of particles as detectable excitations or a quanta of the underlying quantum fields.... Planck's constant doesn't appear in Einstein equations so you won't find anything quantummechanical from them. here are a few views I like to get you started: tomstoer[I think] Marcus: One recent discussion including energy is here : http://www.physicsforums.com/showthr...=photon+energy There is a long and valuable discussion here...at least I learned a lot from it: What is a particle http://www.physicsforums.com/showthread.php?t=386051 Youll find some great illustrations of these in Wikipedia under ATOMIC ORBITAL. http://en.wikipedia.org/wiki/Atomic_orbital be sure to scroll down the page as there as a number of interesting illustrations. 



#5
Dec2013, 06:22 AM

Sci Advisor
P: 1,465

A photon with a perfectly known position will have an arbitrary frequency. Conversely, a photon with a perfectly known frequency will have an arbitrary position. This property is linked to the linearity of waves and the Fourier transform relationships between quantities like time and frequency. Claude. 



#6
Dec2013, 07:54 AM

P: 35





#7
Dec2013, 07:57 AM

P: 5,634

That's a really nice synopsis from Claude if you have been exposed to Fourier analysis...
If you are interested in additional insights, see this discussion "How big is a photon." http://www.physicsforums.com/showthread.php?t=657264 It's long and involved, but if you plow through it you'll really find out the subtelies of 'particles'....read different/conflicting views Here is a quote I like from a famous scientist [maybe in the second link of the prior post above]: Carlo Rovelli: 



#8
Dec2013, 08:48 AM

P: 5,634

HUP is another quantum phenomena whose 'meaning' [interpretation] is still debated..... Just search the that name in these forums and you will find dozens of discussions/arguments/viewpoints. 



#9
Dec2013, 07:33 PM

Sci Advisor
P: 2,470

Quantum Field Theory would say that no, a photon has an exact frequency and an exact position. But the uncertainty is in which photon you are observing. (A photon with which frequency, and at what location.) It's just semantics when you deal with a single particle, but becomes important when you consider manyparticle systems. Just thought you should know that's out there, because you might run into statements about photons with exact frequency and location on this forum or in textbooks, and it might be confusing. 


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