How to find equipotential surface for given case?

[Dexter Neutron]

Q:- Describe equipotential surface due to a uniform grid consisting of long equally spaced parallel charged wires in a plane.
The answer given in my textbook is - Equipotential surface have shape which changes periodically. At far off distances it becomes parallel to the plane.

Why the equipotential surface changes periodically here?Please Explain.
Any help would be appreciated.

 

[nuclear_chris]

I can answer the second question. At far off distances the grid should look like a uniformly charged plane. This results in the potential being equivalent to that of a uniformly charged plane.

 

[DrStupid]

Why the equipotential surface changes periodically here?

Because the charge distribution changes periodical (wire - no wire - wire - no wire - ...).