Two Lenses

\usepackage{optikz}

\begin{tikzpicture}[scale=0.7]
  \draw[very thick, -{latex}] (0,0) -- (5,0);
  \convexlens[angle=0, width=0.5] at (1.5,0);
  \convexlens[angle=0, width=0.5] at (3.5,0);
\end{tikzpicture}