Lecture 22, ACT 3

• Suppose the electric field in an e-m wave is given by:

• In what direction is this wave traveling ?

(a) + z direction

(b) -z direction

• Which of the following expressions describes the magnetic field associated with this wave?

(a) Bx = -(Eo/c)cos(kz + wt)

(b) Bx = +(Eo/c)cos(kz - wt)

(c) Bx = +(Eo/c)sin(kz - wt)

• B is in phase with E and has direction determined from:

• At t=0, z=0, Ey = -Eo

• Therefore at t=0, z=0,

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