Derivation/origin of two equations

[thewall12]

I've encountered two equations and I'm not sure of their origins. First, there's a differential equation describing the amplitude of a scattered electric field, E=(1/(c^2*r))*dp/dt sin y, where p is the scattered dipole moment and gamma (y) is the angle between the dipole moment and line of sight. The equation makes enough sense, I guess. I'm just not able to find any literature on it or its origin. Also, I'm not sure where the equation for the scattered dipole moment, p=po*exp(-ik(r-ct)), comes from. The r indicates that the dipole is oscillating in space, but if it's a dipole particle it can only oscillate in time, correct?

 

[thewall12]

Please help. I'm in desperate need of an answer for this problem I have.