The electric field (in $\mathrm{NC}^{-1}$ ) in an electromagnetic wave is given by $E=50 \sin \omega\left(t-\frac{x}{c}\right)$. The energy stored in a cylinder of cross - section $10 cm^2$ and length 100 cm along the x - axis will be:
Answer & explanation
Correct answer: option 2
Energy contained in a cylinder
u = average energy density × volume
$=\frac{1}{2} \varepsilon_0 \mathrm{E}_0^2 \times \mathrm{A} l $
$=\frac{1}{2} \times\left(8.85 \times 10^{-12}\right) \times(50)^2 \times\left(10 \times 10^{-4}\right) \times 1 $
$= 1.1 \times 10^{-11} J$