Thursday 30 August 2018

photons - How does the frequency of a particle manifest itself?



In terms of wave-particle duality for, let's say a photon; how would the frequency practically manifest/demonstrate itself? Like, i understand that the frequency is related to the energy a particle has, but frequency in my mind suggests oscillation about a point. Is the photon physically oscillating through space as it travels? I wouldnt imagine so. Which periodic occurrence is referred to when one talks about the frequency of a particle?



Answer




Is the photon physically oscillating through space as it travels? I wouldnt imagine so. Which periodic occurrence is referred to when one talks about the frequency of a particle?



No the photon is not oscillating through space. It is an elementary particle of the standard model which is the quantum mechanical description of most of our experimental knowledge on elementary particle to date. Elementary particles are point particles.


The classical wave is built up from an enormous number of photons and as physics theories have to be consistent when the parameters and variables change from microscopic to macroscopic the frequency entering the E=h*nu for the individual photon is the frequency built up in a coherent classical beam emerging from a large ensemble of photons.


Conversely, when one starts with a classical coherent beam of frequency nu, as discussed in the other answer, and one goes to the microscopic level of individual quanta that compose the beam, the photons, the frequency identifies the quantum of energy the photon carries.


For example, a large number of excited atoms at the same energy level ( lasers for example) de exciting to photons will have the energy h*nu that builds up the classical wave.


For what is a particle in the quantum mechanical microcosm see my answer here.



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