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Polynting vectors vecS is defined as a v...

Polynting vectors `vecS` is defined as a vector whose magnitude is equal to the wave intensity and whose direction is along the direction of wave propogation. Mathematically, it is given by `vecS=1/(mu_0) vecExxvecB`. Show the nature of `S` vs `t` graph

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Let us consider that an electromagnetic wave is propagating along the Z - axis . The general expressions for ` vecE and vecB ` are given as
`vecE = E_0 sin ( k x - omega t ) hatj`
` vecB =B_0 sin ( kx - omega t) hatk `
poynthin vector ` vecS` is given by
` vecS = (1)/(mu _0 ) vecE xx vecB `
`= (1)/(mu _0 ) [ E_0 B_0 sin^2 ( kx - omega t ) hati `
The variation of ` | vecS |` vs t graph is shown below :
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