Re: [Phys-L] Radiated power formula -- scaling laws (comment)

[Moses Fayngold <moshfarlan@yahoo.com>]

I want to make a brief comment on JD's post https://www.av8n.com/physics/lienard-wiechert.htm  ;  It explains nicely the EM potentials by using the space-time diagrams. But there is one point there which, in my view, needs correction. Namely, on Fri, Apr. 1, 2016, JD wrote:  
> So some profound questions remain:   
   - Can we take the low-frequency limit of the radiation field and recover the Coulomb field?
   - Can we wiggle the Coulomb field and thereby produce the radiation field?
   - Or are these fields related in some other way?
> The short answers are (a) no, (b) no, and (c) yes.>The only way to explain the two behaviors is to realize that there are two different contributions to the field, one of which is > dominant at short distances and long times, while the other is dominant at long distances and high frequencies. 
I think, question 2. (that is, (b) for consistency with labeled answers) here is ill-posed. One cannot wiggle the Coulomb field. We can only wiggle the source producing field, in the given case - the point charge. So, question 2./(b) should be formulated as:"(b) Can we wiggle a point charge and thereby produce radiation field?" And my answer to this would be (b) Yes. The generated radiation field would be a special case of what we call "Dipole radiation".
Moses Fayngold,NJIT
   
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