Heat And Thermodynamics

Two rods of different metals have coefficients of linear expansion '\(\alpha_1\)' and '\(\alpha_2\)' respectvely. Their respective lengths are '\(\mathrm{L}_1\)' and '\(\mathrm{L}_2\)'. At all temperatures (\(\mathrm{L}_2-\mathrm{L}_1\)) is same. The correct relation is