1.

Magnitude of an electromagnetic wave is E=4.24 sin [(7.54xx10^(6))(t-(x)/(3xx10^(8)))](mV)/(m).Then energy density associated with magnetic field of this wave is ……. (a) 796xx10^(-19) J (b) 796xx10^(-19) J//m^(3) (c) 7.96xx10^(-19) J//m^(3) (d)796xx10^(-19) W

Answer»

`796xx10^(-19)J`
`796xx10^(-19)J//m^(3)`
`7.96xx10^(-19)J//m^(3)`
`796xx10^(-19)W`

Solution :Here, `E_(m)=4.24(MV)/(m)`
`therefore E_(rms)=(E_(m))/(sqrt(2))=(4.24)/(1.414)=2.998 (mV)/(m)`
`therefore E_(rms)~~ 3xx10^(-3)(V)/(m)`
Now energy density,
`RHO = epsilon_(0)E_(rms)^(2)`
`=8.85xx10^(-12)xx(3xx10^(-3))^(2)`
`= 7.9.65xx10^(-18)~~ 796xx10^(-19)J//m^(3)`


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