# The electric field in an electromagnetic wave is given by $E = 50N/C\: \sin \omega (t-x/c)$. Find the energy contained in a cylinder of cross-section $10cm^2$ and length 50 cm along the x-axis.
$\begin {array} {1 1} (a)\;55 \times 10^{-12}J & \quad (b)\;5.5 \times 10^{-12}J \\ (c)\;55 \times 10^{-10}J & \quad (d)\;5.5 \times 10^{-10}J \end {array}$