Question

Electromagnetic WAVES dont need medium to travel ......why??

Answer 1

electromagnetic wave is the wave of electric and magnetic field need no medium to travel although it can travel through transparent medium

Answer 2

reason??

Answer 3

Normal waves need a medium right?? so that adjacent molecules go on disturbing the next molecule,,,forming a pulse,,,(wave)

Answer 4

This is what i know.....changing electric and magnetic fields produce each other in a time varying fashion .......but why do they MOVE forward?? i mean HOW?

Answer 5

i agree that the fields must increase and decrease with time....fine...simple OSCILLATION,,, why do they have to move front?? cant they simply oscillate where they are?

Answer 6

up and down,,,up and down ,,so on....

Answer 7

Electromagnetic waves travel through a vacuum and any other physical medium slows or stops their progression. They do not use existing magnetic fields as a medium, though they do interact with them.

An electromagnetic wave is nothing more than an a propagation of a changing electric and magnetic field. these fields are always perpendicular to each other and travel in the direction of E x B, where E and B are vectors indicating the direction of these fields.

Its because these are electric and magnetic fields. These fields are just regions where forces are exerted on charged particles, they are not made of particles themselves in the same way that sound waves are made from air molecules.

Answer 8

Why do they propagate?

Answer 9

Because the particles experience a force due to the fields. they will have to move.

Answer 10

But there are no particles in vacuum!

Answer 11

i mean , even charged particles are absent in vacuum right?

Answer 12

The field is created by charged particles only. So they do exist.

Answer 13

But like i said, it is not right to term them particles. They are just charged entities that produce a magnetic field.

Answer 14

i dont think so........the sun is the source of the electromagnetic wave(light) and it is said that changing electric fields create changing magnetic fields,,,,,and that keeps on happening till the wave reaches us (earth).......

Answer 15

Sun has charged particles.

Answer 16

But i wanted to know HOW the wave MOVES? how it reaches us??? my question is quite absurd......yet im confused

Answer 17

It is the tendency of every field to move because a charged particle keeps on producing the field.

Answer 18

to produce a electromagnetic wave u need to oscillate a charged particle ....that will create a changing electric field.....now this changing electric field creates changing magnetic field,,,,now this changing magnetic field creates changing eleectric field.....and that goes on....and on ...and on.....But its not necessary to oscillate the charge all the time....its enough if u oscillate it even once!

Answer 19

@CliffSedge can i get some help here??? please

Answer 20

It can be hard to explain without getting deep into the differential equations involved, but here's the gist:

It is a consequence of Ampere's Law and Faraday's Law. (These were synthesized by Maxwell in his famous equations).

Ampere's Law states that a changing electric field generates a magnetic field; Faraday's states that a changing magnetic field produces an electric field.

This process can sustain itself and continue forever.

Answer 21

Applying Faraday's Law to a region with an electric field that changes with distance, a magnetic field is produces perpendicular to the plane of the E-field lines (right-hand rule).

You can calculate the magnetic flux term in Faraday's Law and set its rate of change with time equal to the rate of change of the electric field with space.

\[\delta E/\delta x = - \delta B/\delta t\]

Answer 22

You can do a similar thing with Ampere's Law to get
\[\delta B/\delta x = -\mu \epsilon \delta E/\delta t\]
Differentiating the first equation with distance and the second with time yields a second-order differential equation relating the change in position to the change in time of the electric field.

The solution of this differential equation is a wave that propagates through space at the speed of light.

Answer 23

That's the mathematics that predicts it anyway, as for the physical reason *why* it happens? I dunno. Electricity and magnetism are two halves of the same phenomenon created by moving charges. If the charges are moving through space and time, then the waves they generate move through space and time.

Answer 24

ThanKs a lot!

Answer 25

There is an app java.. but i can't find it now..
in that you can oscillate a charge yourself.. and see how the E M waves propogate..


the basic idea is

When u accelerate a charge, you would expect the field configuration to change immediately right?
For example.. if a point positive charge is A, then the field lines are radially outwards from point A, and now if you move it to B , then you would predict that the field lines show now be radially outwards from point B... however, field lines FAAAAR away, take some finite time to change, they can't change instantly cause INFORMATION TAKES TIME TO TRAVEl... nothing can beat speed of light remember?

That information travels as a wave.. damn.. that app was good

Answer 26

http://www.tapir.caltech.edu/~teviet/Waves/empulse.html

see this site..

Answer 27

Thanks a lot !!!!!!