Electromagnetic wave: Difference between revisions
imported>Paul Wormer (New page: [[Image:Electromagnetic wave.png|center|thumb|550px|Electromagnetic wave. Electric component (red) in plane of drawing; magnetic component (blue) in orthogonal plane; propagation to the ri...) |
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[[Image:Electromagnetic wave.png|center|thumb|550px|Electromagnetic wave. Electric component (red) in plane of drawing; magnetic component (blue) in orthogonal plane; propagation to the right. ]] | [[Image:Electromagnetic wave.png|center|thumb|550px|Electromagnetic wave. Electric component (red) in plane of drawing; magnetic component (blue) in orthogonal plane; propagation to the right. ]] | ||
In [[physics]], an '''electromagnetic wave''' is a change, periodic in space and time, of an [[electric field]] '''E'''('''r''',''t'') and a [[magnetic field]] '''B'''('''r''',''t''). In the figure we see a snapshot (i.e., a picture at a certain point in time) of the magnetic and electric fields in adjacent points of space. In each point, '''E''' is perpendicular to '''B'''. The wave propagates to the right, along an axis which we conveniently refer to as ''x''-axis. Assume the snapshot is taken at time ''t'', then at a point ''x'' we see an arrow of certain length representing '''E'''(''x'',''t''). At a point in time Δ ''t'' later the same value of '''E''' (same arrow) is seen at ''x'' + ''c'' Δ ''t''. The arrow seems to have propagated to the right with a speed ''c''. For ''all'' kinds of electromagnetic waves (see below) the propagation speed ''c'' is the [[speed of light]]. | |||
'''To be continued''' | '''To be continued''' | ||
Revision as of 11:18, 10 August 2008
In physics, an electromagnetic wave is a change, periodic in space and time, of an electric field E(r,t) and a magnetic field B(r,t). In the figure we see a snapshot (i.e., a picture at a certain point in time) of the magnetic and electric fields in adjacent points of space. In each point, E is perpendicular to B. The wave propagates to the right, along an axis which we conveniently refer to as x-axis. Assume the snapshot is taken at time t, then at a point x we see an arrow of certain length representing E(x,t). At a point in time Δ t later the same value of E (same arrow) is seen at x + c Δ t. The arrow seems to have propagated to the right with a speed c. For all kinds of electromagnetic waves (see below) the propagation speed c is the speed of light.
To be continued