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Name: Neil
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Question:
I have read a very little on electron proton interaction and have a question on intersize particle interaction. I am just wondering. Can an electron (electrons being so much smaller than protons) which is travelling near the speed of light 'push' a proton? Further down, how does a single photon, which is so much smaller than an electron, manage to 'push' that much bigger electron out of orbit?



Replies:
Neil,

These are good questions you ask. The answers lie in the different types of forces and energies. While an electron and a proton have very different masses and volumes, their electrical charge is equal in magnitude but opposite in direction. If you confer the concept of momentum onto an electrical charge, then a proton and electron have equal but opposite electrical momentum.

It is a similar concept with a photon and electron. A photon has a zero net electrical charge, but is composed of electromagnetic and mechanical energy. An electron does not get pushed out of orbit by a photon, per se, rather the electron absorbs the photon's energy exactly like food absorbs thermal energy in a microwave. It is all part of the same electromagnetic radiation spectrum. When this absorption occurs, the electron increases in energy and moves further away from a given nucleus.

To be sure, I cannot answer your question completely on why this happens. A point that I would next bring up is since an electron is moving at the speed of light, its kinetic (mechanical) energy cannot increase since it cannot move faster. There must be a gain in another type of energy, which I would assume is either potential or thermal. The key concept of your question is to understand that there are different types of energy, thermal (heat), mechanical (motion--kinetic and potential), chemical, nuclear, gravitational and electromagnetic.

A good example of conversion of one type of energy to another is the mixture of baking soda (sodium bicarbonate) with vinegar (acetic acid). This is a great way to show the release of chemical energy into thermal and mechanical energy. And of course an atomic bomb is another good example of energy conversion. Nuclear energy converts small amounts of matter (mass) into intense thermal and electromagnetic energy (radiation).

Matt Voss



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