Solution

In lanthenoid $$4f$$ orbital is present in low lying level while in actinoids $$5f$$ orbital is there. As $$5f$$ orbital has poor shielding value than $$4f$$ orbital $$\therefore$$ $$Z_{eff}$$ = z- $$ \sigma$$ ($$ \sigma$$ is shielding constant ) is more for $$5f$$ than $$4f$$. More the $$Z_{eff}$$ more will be contraction in size. $$\therefore$$ actinoid contraction is more than lanthenoid contraction.