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# An E.m wave with poynting vector $6\;walt/m^2$ absorbed by a surface of area $12\;m^2$ Find the force on the surface .

$\begin{array}{1 1} 24 \times 10^{-8}\;N \\24 \times 10^{-4}\;N \\ 24 \times 10^{-2}\;N \\ 24 \times 10^{8}\;N \end{array}$

$F= PA$ But $P= \large\frac{I}{C}$
$\therefore = \large\frac{IA}{C}$
$\qquad= \large\frac{6 \times 12}{3 \times 100}$
$\qquad= 24 \times 10^{-8}\;N$