L1 is the length between two adjacent carbon atoms in a layer and L2 is the length in between two layers of graphite. The approximate ratio between L1 and L2 is

→The C—C bondlength in graphite is 1.42Ao [L1]→The graphite has layer like structure, the adjacent layers are held by weak vander waal's forces of attraction→ The distance between the adjacent layers is 3.35Ao (L2 )→ Then L1 : L2 ratio is 1.42Ao : 3.35Ao