  A recent experiment [W. A. Shelton {\emph{et\ al.}}, Phys.\ Rev.\ E
{\bf{71}}, 036204 (2005)] measured the response of a nanorod trapped in a
viscous fluid to the torque produced by an incident optical frequency
electromagnetic wave. The nonlinear differential equation describing this
motion is similar that of a damped, driven pendulum. The overdamped limit of
this equation has been solved analytically. We analyze the properties of this
solution in comparison to the observations of the experiment and find very
close agreement.
