[SOLVED] Retarded Scaler Potantial

Hi,

In my Electromagnetics Theory book, wave equations have attached solution, where Spherical coordinate system is used and R is distance, Up is the velocity of wave propagation, pv is charge density of the volume.:

Can someone tell me how to use (t-R/up) term in this equation? I mean V is time dependent and at time 0, we have 0 potantial and at infinity, we have infinite potantial?

Thanks.

pv is a function of time. The topic can be closed.