Interference by electric field

[A Dhingra]

interference by electric field...

first thing, is it possible?

i was thinking , if we have a stationary charge and an oppositely charged plate with a small gap in it... and behind that plate, a screen is placed to obtain the patterns so obtained by the electric field passing through that gap... in this type of an apparatus... i was wondering if the pattern obtained on the screen be similar to that obtained by interference (due to bending by diffraction.) of light...

here i was thinking that the electric field is similar to the wavefronts described by Huygens and hence the gap in the plate should behave as a new source of electric field that moves in all the directions... as such behaving as a new charge present at the gap.
so can you tell me what would the result be like?

also if this is possible, i had an idea that may be that's what a moving electron does... causing it to behave like a wave ( but this sounds very silly!)

thanks...

 

[Drakkith]

and behind that plate, a screen is placed to obtain the patterns so obtained by the electric field passing through that gap

I don't think an electric field produces patterns. But I'm not sure. Would two sources of an electric field produce an interference pattern? Again, I don't think so, but I don't know enough to say either way for sure.

 

[A Dhingra]

... can you tell me if the assumption that electric field behaves as a wavefront correct... though it does not move...
(in a way it does when a charge is created ,be it in a pair..)
and can electric field bend like light does?
(ultimately light is electric and magnetic field... )

 

[Drakkith]

... can you tell me if the assumption that electric field behaves as a wavefront correct... though it does not move...
(in a way it does when a charge is created ,be it in a pair..)
and can electric field bend like light does?
(ultimately light is electric and magnetic field... )

I can't, I do not know enough about the subject. I've never heard of the electric charge moving like a wave, but I'm no expert here.

 

[A Dhingra]

can you suggest, which subject this topic will fall under...??
and some related books as well...

anyone else, with something about this...!

 

[sophiecentaur]

Huygens:
This method applies to Waves - not to static situations. To find the field pattern of a charged object, you can look, point by point, at the potentials from every piece of the object and add them together. Having obtained this pattern of potential around the object, you can then plot equi-potential contours (surfaces, as it's a 3D problem). The 'field lines' can then be constructed by drawing curves that intersect the equi-potential surfaces.

If you can't get what I'm saying then think of gravity. Around the Earth, you can construct a set of spherical shells around the surface (because it's a symmetrical object). The gravity field lines are, of course, a set of straight lines, radiating from the centre (each on is at right angles to the spherical shells). Those lines will be the paths of falling objects.

 

[The_Duck]

Static electric fields don't diffract like traveling waves do. You can't get them to make an interference pattern. To determine the electric field from some array of static electric charges, you simply calculate the field from each charge and add up all the fields at each point. Perhaps given this you can convince yourself that there's nothing like diffraction, since the plate does not "block" the field of the other charge in any way. Rather, the stationary charge and the oppositely charged plate both produce electric fields which add together.

Static fields and wave fields behave differently. While they both arise from Maxwell's equations, a static electric potential is a solution to Poisson's equation, while the electric and magnetic potentials that describe an electromagnetic wave are solutions of the wave equation. These are two different differential equations whose solutions display qualitatively different behavior.

To learn about this stuff I'd start with the E&M sections of a freshman general physics textbook like Halliday, Resnick, and Walker and then go to an undergrad E&M textbook like Griffiths. You'll need multivariable calculus for the latter.

 

[sophiecentaur]

Waves have different phases in different places and that causes constructive and destructive interference, depending on where you are. Static fields have no (the same) 'phase' everywhere so they just add up vectorially.

 

[A Dhingra]

yes true electric field has no phase difference, so this kind of a phenomenon is not possible... and it is not a wave...

but if the apparatus of young's double slit experiment is used, will there be any of the desired results?

 

[sophiecentaur]

Young's slits work because of a Path Difference from two sources to a point on the screen which produces difference phases for the two contributions. If there is no Frequency, then there can be no Phase so there can be no interference. The fields will always JUST ADD UP arithmetically.
Just look at how the pattern of the Young's Slits experiment is derived (google). How could you possibly get interference from a static situation?

You appear to be just repeating your initial question, Why? The answer will always be the same.

 

[A Dhingra]

alright...
i got the fact that electric field is stationary...
though i can prove it not to be always stationary...
with that thought i was thinking this way , but fine.

and i repeat the question in different forms because i like to think about a same situation from various possible options( i know here it was too much..)

 

[sophiecentaur]

You originally described a static situation. How would the Electric Field be changing?
If it is changing (and not a static field) then you could have interference, which would depend on the wavelength of the resulting radiated field - and, for a non-sinusoidal wave / step change or impulse, some very complicated field distribution which would be changing with time.
But you just changed the goalposts.

 

[A Dhingra]

i am sorry... i actually described the static situation at all the places and kept confusing...
what i started with was that, the charges are stationary, but that does not necessarily mean the field is also stationary...
but i didn't mention the later part...

now finally i want to know if a newly formed charge (be ti in pair, pair production, if it is real) will have the field moving such that it reaches to infinity...( probably with the speed of light...)ultimately a moving field...

and the interference pattern related to that. ( the previous question will automatically answer it right?)
thanks a lot for hearing to all my silly ideas and replying as well...

 

[sophiecentaur]

The interference in the Young's Slits setup refers to what happens with a coherent, monochromatic source of waves (i.e. an infinitely long train of repeated waves). You are discussing the effect during a step transition. This would be time dependent as well as space dependent and, whilst it could be worked out, is not what Young was talking about.