# Physical meaning of parts of electromagnetic wave

by littlepapa87
Tags: electromagnetic wave
 P: 4 in E = E_0exp i(k dot r - wt) or E = cos(k dot r - wt) what does k dot r physically represent? Can r be any position in space or must it lie on the wave? (I physically understand what a dot product is)
 P: 674 That's a plane wave, it occupies all of space. If you want a beam that is localized along a line, E_0 has to be a function of distance from the line.
Mentor
P: 11,864
 Quote by littlepapa87 Can r be any position in space
Yes.

 or must it lie on the wave?
A 3-dimensional plane wave fills space. It doesn't lie "along" a line or other single path. See the diagram and associated instructions in the following post for a more realistic picture of a plane electromagnetic wave than you see in many textbooks.

http://www.physicsforums.com/showpos...90&postcount=6

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