# Electromagnetic field in vertical

1. Oct 24, 2012

### scientifico

Hello, I know the electromagnetic field propagates in a 3D space so if I am horizontally aligned with the field I will receive its variation but what if I'm vertically aligned ?

thanks

2. Oct 24, 2012

### AJ Bentley

It isn't clear what you mean.

Are you talking about Electric Field, Magnetic Field or Electromagnetic Waves?

3. Oct 24, 2012

### scientifico

electromagnetic waves

4. Oct 24, 2012

### Drakkith

Staff Emeritus
Are you asking what happens if the orientation of the EM waves electric field changes with respect to you? (Let's use antenna instead of you)

5. Oct 24, 2012

### scientifico

yes an antenna put about horizontally compared to the charge will receive the em field variations bat what if the antenna is above it ?

6. Oct 24, 2012

### Drakkith

Staff Emeritus
I don't understand what you mean by "above it". It sounds like you think the EM wave is a squiggly line that travels through the air. This is not true. It is a wavefront that, in an omnidirectional transmitter, is emitted in all directions. This is similar to dropping a rock in water. The waves make a circle as they travel outwards known as a wavefront, and an EM wave makes a spherical wavefront in this case.

The EM wave diagram or graph that you see everywhere represents the vector of the electric and magnetic fields. This just means that as the wave passes over an object, it will push charges in one direction, then stop and push the other way before stopping again and repeating the process. The orientation of the electric field is known as polarization.

7. Oct 26, 2012

### scientifico

By above it I mean a situation like this. will antenna 1 receive nothing ?

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8. Oct 26, 2012

### Drakkith

Staff Emeritus
This is exactly what I thought you were getting at. Like I said above, that diagram is not what you think it is. The X and Y axis are amplitudes, while the Z is either time or distance. This is only showing you the relationship between phase, amplitude, and the orientation of the VECTOR of the fields. Read my post above again.

An EM wave expands outward in all directions. If it is an omnidirectional emitter the wave will expand outwards in a spherical shape. Again, think of a rock making ripples in a pond, but instead of the 2d ripples that make circles, Em waves make spheres. (Or cones or some other 3d shape depending on the circumstance)

9. Oct 28, 2012

### scientifico

so does the charge vibrate in all directions not just up and down ?

10. Oct 28, 2012

### Drakkith

Staff Emeritus
That depends on the polarization I think, not sure.

11. Nov 15, 2012

### scientifico

do you know any video which could help me in visualizing and understanding Em waves correctly ?

12. Nov 16, 2012

### andrien

when an electromagnetic wave falls on a charged particle,then the electric field will accelerate it and it gets a velocity in that direction .After it,magnetic field will act because it can not not act if particle does not have a velocity.The magnetic field exerts the force on the charge particle in the direction of propagation of wave,as is easily seen because of lorentz force law.So it is only the E field which will cause the oscillatory motion in up and down direction and that is what is meant by polarization of EM wave.