168- An object moves at a constant speed toward a converging lens. If at a certain moment the object is at a distance $2f$ from the lens, and the position changes so that the object moves from distance $2f$ to distance $f$ from the lens, how does the image move? (f is the focal length of the lens.)
[(1)] It moves away from the lens slowly.
[(2)] It moves away from the lens quickly.
[(3)] It moves toward the lens slowly.
[(4)] It moves toward the lens quickly.
\textbf{168-} An object moves at a constant speed toward a converging lens. If at a certain moment the object is at a distance $2f$ from the lens, and the position changes so that the object moves from distance $2f$ to distance $f$ from the lens, how does the image move? (f is the focal length of the lens.)
\begin{itemize}
\item[(1)] It moves away from the lens slowly.
\item[(2)] It moves away from the lens quickly.
\item[(3)] It moves toward the lens slowly.
\item[(4)] It moves toward the lens quickly.
\end{itemize}