Electromagnetic waves: Photons generated by two charges attracted to each other?

[frustrationboltzmann]

Hello all,

after thinking about properties of electromagnetic waves, especially concerning the electric field of them, I ran into some serious understanding problems:

1) photons are electromagnetic waves and vice versa and they convey electrical force. Let's now do a thought experiment: let's assume 2 free charges in vacuum, which attract each other. let's say an electron and a proton a little distance from each other. when they attract each other the electric field vector has to lie on the "line" connecting them, in order to accelerate the 2 particles to each other. the conveying photons are now sent on the same line between the particles...but wait, now the k-vector and the E-vector of the electric field would be not normal to each other, like maxwell´s equations would assume but parallel. how can this work without contradiction or did I understand some aspect wrongly?

 

[Nugatory]

You are misunderstanding the relationship between photons and electromagnetic waves; photons do not work anything like the way you're thinking. Although they are "the carriers of the electrical force" that doesn't mean what it sounds like; they don't move between two charged particles being attracted or repelled by electrical forces. They are not electromagnetic waves and electromagnetic waves are not made up of a stream of photons flowing by.

There's no really good way of describing what a photon is in a B-level thread; the simplest remotely reasonable explanation that I know of is http://www.physics.usu.edu/torre/3700_Spring_2015/What_is_a_photon.pdf, and the mathematical price of admission is substantial. http://math.ucr.edu/home/baez/photon/schmoton.htm is also a good read, as is http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html (this one addresses the connection between photon exchange and electromagnetic forces most directly). You'll also find some pretty good informal descriptions in some of our older threads if you search around.

You only need to consider photons when working with problems in which quantum mechanical effects are significant. You have to completely understand electromagnetic waves using Maxwell's equations and other classical methods before you can start thinking about photons.

 

[sophiecentaur]

1) photons are electromagnetic waves and vice versa

You really must try to unlearn that idea. EM energy can be treated in terms of waves or in terms of photons, depending which is more convenient at the time. The 'duality' notion that's still popular with non-physicists these days, actually died a death several decades ago. A photon cannot be given a valid description using waves, and vice versa.
Read what @Nugatory says above.

 

[Drakkith]

when they attract each other the electric field vector has to lie on the "line" connecting them, in order to accelerate the 2 particles to each other. the conveying photons are now sent on the same line between the particles...but wait, now the k-vector and the E-vector of the electric field would be not normal to each other, like maxwell´s equations would assume but parallel. how can this work without contradiction or did I understand some aspect wrongly?

I wouldn't even attempt to understand forces in terms of photons without first spending a significant amount of time learning about quantum electrodynamics and its underlying math. Ordinary language and experience is woefully inadequate to explain this using photons, so you must spend time learning at least a little bit of a new language (that of QED and its math) and getting some experience in accurately understanding various quantum phenomenon. And note that when I say 'accurate', I mean it. Watching a few youtube videos will not cut it.

Here's a good site to start with: https://profmattstrassler.com/artic...-basics/fields-and-their-particles-with-math/

There are dozens of short articles on various aspects of particle physics on that site. Just use the drop down menu at the top labeled 'Articles'.