Capacitors with multiple dielectrics

[jordanjj]

Ok so I know that multiple dielectrics inserted into the space between two plates one on top of the other and not side by side should be treated as capacitors in series and the overall capacitance should be calculated this way but why? I can't find the theory behind this anywhere in my text.

 

[epenguin]

I don't have any text that says anything about that, but I don't need one. Think physically, maybe a thought experiment, you need no maths. Think how you get from this multisandwich to a series of capacitors.