Re: [Phys-l] Electromagnetic waves

[curtis osterhoudt <flutzpah@yahoo.com>]

My own thoughts on this (the question applies as well to gravity waves, and wavefunctions, though I find the resolution in those cases to be even more mysterious) parallel Feynman's (and, if I remember correctly, Griffiths') explanation: The inertial and restoring forces are both taken care of by the collapse of the co-traveling magnetic field (remember that half the energy is in the B-field in a vacuum; half is in the E-field); induction says that this change prompts the growth of the E-field. When the E-field decays, this prompts the growth of the B-field.

  Of course, I don't know how "simple" an answer is required. Propagating E&M waves carry their own restoring force with them!

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Down with categorical imperative!
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________________________________
From: ludwik kowalski <kowalskil@mail.montclair.edu>
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Sent: Sun, February 28, 2010 10:26:13 AM
Subject: [Phys-l] Electromagnetic waves

I was asked a simple question. How can it be answered in a simple way?

> "For a wave to form, a restoring force is required. For example, the  
> sound waves in air are produce by compressing the air and the  
> restoring force is related to the compressibility of the gas. What  
> is the restoring force for radio waves in a vacuum?"



Ludwik Kowalski
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