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**The "Wave Zone" Definition**

Hello!

We are trying to figure out exactly what the "Wave Zone" is when considering potentials.

We know that a moving charge will generate a "disturbance" in the surrounding fields, which propagates outwards at light speed.

This means that for great distances from the source, observations made will involve the potentials for earlier times, as the speed of light is finite. Therefore you would want to evaluate the "retarded time" which is the time delay in the light reaching the observer, and it is calculated using

[tex]t' = t - \frac{r}{c}[/tex]

Where r is the extra distance travelled to quantify this time delay......?

In books it says that this is how you evaluate the potentials in "Wave Zones" but we are not clear exactly what this wave zone is? We know that the potential is a function of this retarded time, is it just a scenario when there is a time delay (and so at large distances) ?

Thank you in advance!

Hannah