dielectric slab in some space between a capacitor

karanbir

when we place a dielectric slab between two plates of a capacitor(size small as compared to space between plates), we take it equivalent to 2 capacitors in series- one plate of capacitor and surface of dielectric and other plate of capacitor and surface of dielectric. My question is that a capacitor is formed with two plates having equal and opposite charge but the induced charge on surface of dielectric is less than charge on plates(q(induced)=q(1-1/k)), then how can we consider one plate of capacitor and surface of dielectric as a single capacitor?