E & B fields in EM wave

Thread View: bit.listserv.physhare

1 messages

[T] Back to Threads [V] Tree View [G] Group Articles

1 total messages Started by James E. Hetrick Mon, 16 May 1994 14:54

#1472

Author: James E. Hetrick
Date: Mon, 16 May 1994 14:54

37 lines
1695 bytes

Sorry I can't quote the original poster's message---seems like I
pressed the wrong button this weekend...

Anyway, the question was why E and B fields are in phase in an EM wave
(in free space, away from charges, etc.)

The relevent Maxwell eqs. are:

	curl E + d/dt B = 0

	curl B - d/dt E = 0

in natural units (c=1).

From these we see that the _space derivative_ of B is equal to the
_time derivative_ of E (not E itself, if I recall the posted question
correctly).

Given that E & B are plane waves:

	E = E_0 exp{ i w (t - z) } x^
	B = B_0 exp{ i w (t - z) } y^

say, for a plane wave moving in the z^ direction, substitution into 
Maxwell's eqs. gives 

	E/B = 1  (really E/B = c, putting c back in)

So that B must follow E and vice versa.

--Jim


--
<>--------------------------------------------------------------------<>
      James E. Hetrick            Institute for Theoretical Physics
     hetrick@phys.uva.nl               University of Amsterdam

Thread Navigation

This is a paginated view of messages in the thread with full content displayed inline.

Messages are displayed in chronological order, with the original post highlighted in green.

Use pagination controls to navigate through all messages in large threads.

Back to All Threads