Answer:
The length of the rod should be
[tex]\frac{L}{4} \\ [/tex]
Explanation:
Period of simple pendulum is given by
[tex]T=2\pi\sqrt{\frac{l}{g}} \\ [/tex]
We have
[tex]\frac{T_1^2}{T_2^2}=\frac{l_1}{l_2}\\\\\frac{2^2}{1^2}=\frac{L}{l_2}\\\\l_2=\frac{L}{4} \\ [/tex]
The length of the rod should be
[tex]\frac{L}{4} \\ [/tex]