# How 'tall' is an electromagnetic wave??

Discussion in 'Wireless & RF Design' started by Paulo540, Nov 18, 2010.

1. ### Paulo540 Thread Starter Member

Nov 23, 2009
188
0
Hey guys,

long time no talk. I can't believe I am asking this but I can't seem to find a really satisfying answer anywhere.

I understand what wavelengths are and that there are two components to a wave that are perpindicular to each other... E and H...

But is there a correlation to the actual physical heigth of the wave? Would this be the magnitude?

I think my problem is I keep trying to put things in a tangible perspective but maybe there isn't one regarding this?

2. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
Take an EM wave radiating from a whip antenna. The radiation pattern is (ideally) in a cylindrical form, starting at the surface of the whip. The radius increases at the sped of light. But that is only in the horizontal plane - there should be no vertical component.

In the case of a horizontal dipole, the cylinder's radius grows so the wave does have a height.

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3. ### BillO Distinguished Member

Nov 24, 2008
992
139
There may be spacial extent in the propagation of the wave, but not in its amplitude. The amplitude is in the extent and manner of perturbance in the associated E and H feilds.

It does not have spacial 'height' like a wave on the surface of water.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Yes you don't have a physical medium which is being waved up and down - so to speak. For example mechanical waves require a medium in which to propagate - like water.

Early physicists believed light propagated in such a medium called the luminiferous aether. This was not supported by experimental evidence.

See http://en.wikipedia.org/wiki/Michelson–Morley_experiment

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5. ### Robin Mitchell Distinguished Member

Oct 25, 2009
821
285
height...
well its dependent on its amplitude. The wave is transverse, lets assume it wave velocity is parallel to the ground, then the heigh is twice the amplitude

6. ### BillO Distinguished Member

Nov 24, 2008
992
139
Maybe a representation on a chalk board, but not in reality. This not a mechanical thing and you need to stop thinking of as such. I see this same error played over and over again.

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7. ### Paulo540 Thread Starter Member

Nov 23, 2009
188
0
I think this is exactly what I was trying to do. It's as though I was expecting to see a scope trace sailing through the air.

Thanks to everyone for their input. It has helped solidify my deep-down sense that I had something wrong.