# Homework Help: What creates EM waves

1. Oct 9, 2012

### aaaa202

My book seems to not go into a lot of details as to how EM-waves are created. More or less they just state that they are created by accelerated charges. I guess that somehow makes sense since an accelerated charge is clearly altering the electric field everywhere in space and that is as far as I can see what creates an electromagnetic disturbance -> electromagnetic wave. But shouldn't a charge moving with constant velocity do the same? And what is an electromagnetic physically? Is it information about the altering of the field spreading out or..

2. Oct 13, 2012

### FeynmanIsCool

Electrons exciting and dropping down to their ground state. The energy that was held by the electron in its excited state needs to go somewhere when the electron jumps back down to its ground state and is released as a packet of energy. This energy is called "quanta" and was latter called a photon. These photons have particle-wave duality (meaning they have characteristics of waves and particles) They act like particles to an extent because we can count them with photo multipliers, but they have wave like properties as well.

What is a electromagnetic wave (physically)?
So under the wave model,
The EM wave is a Transverse wave meaning the wave oscillations are perpendicular the direction of the energy. The EM wave physically is an wave comprised of E and Bfields oscillating in phase perpendicular to each other (where the E field is the bigger of the two) where the frequency of the wave is inversely proportional to the wave length
v=fλ​

If you were to look at the wave from a particle standpoint:
Quanta released from the electrons (Dubbed Photons by Einstein) would be propagated and would have a energy porportional to its frequency by this formula:
E=hf=hc/λ​

Hope this helps!

Last edited: Oct 13, 2012