how the backward traveling Hygen's secondary waves actually get cancelled?

Question

Each point on a primary wavefront serves as the source of spherical secondary wavelets such that the primary wavefront at some later time is the envelope of these wavelets. Moreover, the wavelets advance with a speed and frequency equal to that of the primary wave at each point in space. A s per Huygens principle, only the forward movement of a wave is explained, but the construction will generate a wave travelling back to the source also. In a homogenous medium that is not observed.
How does one explain that? need physical and mathematical explanations (or references)

Answer 1

There are two components to the wave solutions of Maxwell's equations, which describes Huygen's waves, the first is called retarded, the other advanced. Physicists have conventionally dropped the advanced waves as "unphysical". In other words, by fiat, it's not a problem. Otherwise, it is a serious deficiency of Huygen's principle.

Answer 2

Wow! This question has nothing to do with Earth Sciences and Geology! Maybe you should choose the appropriate forum, like Physics.

Answer 3

i dont know