1.

The electric field in an electromagnetic wave is given by `E=( 50N (C^-1)) sin omega (t-x/c).` Find the energy contained in a cylinder of cross section `10 cm^2` and length 50 cm along the x- axis.

Answer» Correct Answer - A::B
`u_E = u_B = 1/2 epsilon_0 E^2`
`= 1/2 epsilon_0 ((E_0)/(sqrt 2))^2`
`=1/4 epsilon _0 E_0^2`
`= 1/4 (8.86 xx 10^-12)(50)^2`
`=5.54 xx 10^-9 J//m^3`
Total energy = `(u_E + u_B)` (Given volume)
`= 2 xx 5.54 xx 10^-9 xx (10 xx 10^-4)(0.50)`
= `5.55 xx 10^-12 J`.


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