A spring whose unstretched length is $l$ has a force constant $k$. The spring is cut into two pieces of unstretched lengths $l _ { 1 }$ and $l _ { 2 }$ where, $l _ { 1 } = n l _ { 2 }$ and $n$ is an integer. The ratio $k _ { 1 } / k _ { 2 }$ of the corresponding force constants, $k _ { 1 }$ and $k _ { 2 }$ will be:\\
(1) $\frac { 1 } { n ^ { 2 } }$\\
(2) $n ^ { 2 }$\\
(3) $n$\\
(4) $\frac { 1 } { n }$