Direction of secondary wavefronts from the point sources

[shivam01anand]

Homework Statement

My question is simple.

Homework Equations

Why do we not take the direction of secondary wavefronts from the point sources to be going backwards to the original direction of the wave as a whole?

The Attempt at a Solution

Thanks to you! :D

 

[mfb]

You can do that, but then you have to do it at every point in space, and as a result those contributions usually* cancel each other.

*you did not give the setup, so it is hard to tell