A pendulum with the time period of 1 s is losing energy due to damping. At a certain time, its energy is 45 J. If after completing 15 oscillations its energy has become 15 J, then its damping constant (in $\mathrm { s } ^ { - 1 }$) will be\\
(1) $\frac { 1 } { 2 }$\\
(2) $\frac { 1 } { 15 } \ln 3$\\
(3) $\frac { 1 } { 30 } \ln 3$\\
(4) 2