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Q & A: light carrying particles

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Most recent answer: 04/20/2011
Q:
Light being a electromagnetic wave is it able to carry paticles through space?
- Joshua Johnson (age 17)
Tahlequah Oklahoma USA
A:
There are two somewhat different ways to interpret that question. I'll try both.

1. Can light push along some other type of particles, say electrons, or maybe little pieces of aluminum foil? The answer is definitely yes. From the early days of Maxwell's electromagnetic theory, it was clear that electromagnetic waves carried momentum. When these waves are absorbed by an object or scattered by one, the momentum change of the wave is transferred to the object. Transferring momentum means exactly the same thing as exerting force.

2. Does the wave itself consist of particles being transmitted? You can think of a light wave as consisting of particles (dubbed photons). So in that sense the wave is itself the flow of particles from one place to another. The picture can be a little misleading, since these photons don't have separate identities and a typical beam doesn't have a well-defined number of them.

Mike W.

(published on 04/20/2011)

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