An electromegnetic plane wave is travelling in the +y direction, its electric fi

Question

An electromegnetic plane wave is travelling in the +y direction, its electric field vector points in the +x direction, and has maximum amplitude Emax with wave vector K and angular frequency w.

a) if the E field vector in the wave assumes its maximal value in the -x direction at y=0 and t=0, write an expression for the E field vector E at all points Y at time t

b) write an expression for the magnetic field vector B at all points y and time t, give both amplitude and direction for B

c) write an expression for poynting vector S at all points y and time t

d) The electromegnetic wave is reflected by a mirror located in the X-Z plane, a scientist wants to balance the pressure on the mirror by shining an electromegnetic wave witht he same frequency from the opposite direction onto the backside of the mirror, which is totally absorbing, which maximum amplitude in terms of Emax, must he choose for the seond wave?

Explanation / Answer

E = - E0 ihat cos( ky - wt)

b) B = E0/c khat cos(ky-wt)

c) S = E0^/c cos(ky-wt)^2 jhat

d) so P = 2 I/c and for absorbing I/c

so would need I to be double

so E = sqrt(2) Emax

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