For a parallel plate capacitor
C = \(\cfrac{kɛ_oa}d\)
where K = dielectric constant
ɛo = permissivity of free space
a = area of plate
d = distance between the plate
C \(\propto\) K
\(\cfrac{C_1}{C_2}\) = \(\cfrac{k}{2k}\)
= then C1 = \(\cfrac{C_2}2\)