An electromagnetic wave from a wire antenna travels (from the reader) toward the

Question

An electromagnetic wave from a wire antenna travels (from the reader) toward the plane of the paper. At time t = 0.0 s it strikes the paper at normal incidence. At point O and t = 0.0 s, the magnetic field vector has its maximum value, 5.07×10-8 T, pointing in the negative y-direction. The frequency of this wave is 1.46×106 Hz.

a. What is the x-component of the associated electric field E at time t = 0.0 s? (Use the right-hand rule to determine the direction of E, and hence the sign of the x-component.)

b. What is the magnitude of the Poynting vector of the wave at time t = 0.0 s?

c. What is the y component of the magnetic field at point O at time 3.42×10-7 s?

Explanation / Answer

We know, B = E/c,

so, E = Bc = 5.07 *10^(-8) * 3 * 10^8 = 15.21 N/C

The wave is travelling along plane of paper and magnetic field is along negative y direction, so, electric field will be along z direction and it its x component at t= 0 sec will be zero.

(b) Poynting vector, S = EH = EB/u0 = 6.14 (u0 = 4*pi*10^(-7) Tm/A)

(c)

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