Imagine two electrons ##A## and ##B## at rest.(adsbygoogle = window.adsbygoogle || []).push({});

Electron ##B## is at a vertical distance ##r## above electron ##A##.

Let us assume that the electrons are constrained to move on horizontal rails.

At time ##t=0## I give electron ##A## a horizontal acceleration ##a## for a time interval ##\Delta t##.

At time ##t=r/c##, due to the impulse provided by the classical Lienard-Weichert radiation field of electron ##A##, electron ##B## gains horizontal momentum:

$$\Delta p = F\Delta t=-\frac{e^2a\Delta t}{4\pi\epsilon_0c^2r}$$

In terms of quantum electrodynamics a photon is exchanged between electron ##A## and electron ##B##.

Therefore if electron ##B## receives a momentum ##\Delta p## from the photon does that mean that electron ##A## must recoil with momentum ##-\Delta p## as it emits the photon?

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# Simple electron recoil question

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