# Re: trying to understand/visualize EM waves. please help

*From*: "Bill Miller" <kt4ye@xxxxxxxxx>*Date*: Fri, 18 Jun 2010 17:35:48 -0400

"John Polasek" <jpolasek@xxxxxxxxxx> wrote in message

news:4qan16dac1brd2rgb4h9j1uq248tgson0o@xxxxxxxxxx

On Fri, 18 Jun 2010 10:14:17 -0400, "Bill Miller" <kt4ye@xxxxxxxxx><snip>

wrote:

You have stated the conditions correctly. But in order for E to cause H toE and H are logically 180° out of phase which can be seen if E and H

cause E...etc. It would be necessary for E and H to be out of phase. But

that would mean that the E/H ratio would have to be a complex number.

The impedance of space is 377 Ohm; not 377 +jX.

are sine waves. Their operations are two derivatives apart, so that

the sine wave of one becomes -omega^2 sine of the other.

Simple analogy: voltage in a capacitor is time integral of current

1/Cint[idt, while the voltage in an inductor is the time derivative

of the current Ldi/dt, 2 derivatives ahead of the capacitor.

In AC parlance, Z = jwL and Z = 1/jwC and Z = R.

At resonance the sum of Z+Z equals 0.

Solve to find w^2 =1/LC.

Like Salmon Egg, you are lettting an inappropriate analogy get in the way.

Let's take your postulate that the electric field and the magnetic field are

180 degrees apart. Let us define the maximum electric field value as E and

the maximum magnetic field value as H. We agree that they are

time-synchronous. And they are both sine waves.

At time T_0, let us agree that E = 0 and H = 0. Now let us move forward in

time by 30 degrees in sine wave time. The electric field amplitude will be

0.5E and the magnetic field amplitude will be - 0.5E. Move forward in time

to 90 degrees. The electric field amplitude is now E and the magnetic field

amplitude is - H.

Question 1: If the electric field and themagnetic field are exchanging

energy, how is it that the energy contained in both the electric field and

the magnetic field have both increased simultaneously? Where did the energy

come from?

We can now proceed to time t advanced by 150 degrees. Now the electric

field magnitude has decrease to 0.5E and the magnetic field has decreased to

*0.5H.

Question 2: If the electric field and themagnetic field are exchanging

energy, how is it that the energy contained in both the electric field and

the magnetic field have both decreased simultaneously? Where did the energy

go?

All the best,

Bill

.

**Follow-Ups**:**Re: trying to understand/visualize EM waves. please help***From:*p . kinsler

**Re: trying to understand/visualize EM waves. please help***From:*glen herrmannsfeldt

**References**:**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*p . kinsler

**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*p . kinsler

**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*Salmon Egg

**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*Salmon Egg

**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*John Polasek

**Re: trying to understand/visualize EM waves. please help***From:*Bill Miller

**Re: trying to understand/visualize EM waves. please help***From:*John Polasek

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