Force on Photon? Interaction with Matter Explained

[bob012345]

TL;DR

Do we speak of forces on photons?

When photon interact with matter there is a force. Do we speak in terms of Newtonian action-reaction? When a photon exerts a force on matter -an action- do we speak of a force on the photon - a reaction? Thanks.

 

[dextercioby]

We cannot speak of forces on photons. The interaction between "matter" and photons (i.e. quantized radiation) cannot be modeled by forces, let alone Newtonian ones.

 

[bob012345]

Thanks. So if light has a pressure on a solar sail, what do we call it? And whatever we call it, then you woud argue that Netwon's Third Law just isn't relevant? Thanks.

 

[bob012345]

In a simple example of two current carrying wires, there are mutual forces. Do we speak of the forces on each wire as action-reaction or as someone I'm debating with, each wire and the photons from the other wire as action-reaction? Or both?

 

[PeterDonis]

So if light has a pressure on a solar sail, what do we call it?

We call it classical physics, not quantum physics. But you put this thread in the quantum physics forum and used the term "photon" in your OP, not "light". Which theoretical framework do you want to use?

If you want to use the classical framework, then you can open a new thread in the Classical Physics forum, not using the term "photon", to ask about how things like solar sails are modeled classically.

If you want to use the quantum framework, then the answer @dextercioby gave is correct.

Either way, this thread is closed.

 

[PeterDonis]

In a simple example of two current carrying wires, there are mutual forces. Do we speak of the forces on each wire as action-reaction or as someone I'm debating with, each wire and the photons from the other wire as action-reaction? Or both?

This question belongs in the Classical Physics forum, not here. Please start a new thread there if you want to discuss it. And again, the term "photon" has no place in a classical physics discussion.

This thread remains closed.