Is it the correct representation of Electromagnetic waves?

[goodname]

Below is the Wikipedia URL shows the shape of EM wave.

http://upload.wikimedia.org/wikipedia/commons/3/35/Onde_electromagnetique.svg"

Electromagnetic laws say that'

"changing magnetic field produce electric field and changing electric field produce magnetic field"

In the representation of EM waves, In an instant, the magnitude of electric field and magnitude of magnetic field at a point in the propagation direction are equal in magnitude but their directions are perpendicular to each other and to the propagation direction. It shows electric field and magnetic field are simultaneously zero at a time and simultaneously maximum at another time.

Both are sinusoidal. Mathematically for sinusoidal waveform, maximum change occurs at zero crossing and minimum change occurs at its peak value. So magnetic field should be maximum when electric filed is zero. Similarly electric filed should be maximum when magnetic filed is zero. This makes 90 degree phase shift in actual EM wave propagation diagram. So which is the correct representation?

 

[Doc Al]

In the representation of EM waves, In an instant, the magnitude of electric field and magnitude of magnetic field at a point in the propagation direction are equal in magnitude but their directions are perpendicular to each other and to the propagation direction. It shows electric field and magnetic field are simultaneously zero at a time and simultaneously maximum at another time.

That--and the diagram you linked--is correct. In a plane EM wave, the magnetic and electric fields are in phase.

Both are sinusoidal. Mathematically for sinusoidal waveform, maximum change occurs at zero crossing and minimum change occurs at its peak value. So magnetic field should be maximum when electric filed is zero. Similarly electric filed should be maximum when magnetic filed is zero. This makes 90 degree phase shift in actual EM wave propagation diagram.

It's not so simple. You have to look to what Maxwell's equations actually say about how changing electric and magnetic fields relate. The curl of the electric field equals the (negative) rate of change of the magnetic field:

<br /> \nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}<br />

When you work out the details, that implies that the magnetic field (B) is in phase with the electric field (E) for a plane sinusoidal wave.

 

[goodname]

Thanks Doc Al

 

[vancerfan]

professional,I do not know what it is,embrassing

 

[Dale]

The curl of the electric field equals the (negative) rate of change of the magnetic field:

<br /> \nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}<br />

When you work out the details, that implies that the magnetic field (B) is in phase with the electric field (E) for a plane sinusoidal wave.

To expand on that a bit, the curl is a measure of how much the E field is changing spatially, that is highest at the zero crossing. Then the time derivative is a measure of how much the B field is changing wrt time, which is also highest at the zero crossing. So they must reach their zero crossings at the same time, which means they are in phase.

 

[AtomicJoe]

I think the OP is thinking of a capacitor or that it might work like a capacitor (not unreasonable) where the change in one field produces the other.However in EM radiation it seem they are directly related to each other not by the rate of change.
http://www.piclist.com/images/www/hobby_elec/e_ckt20_2.htm