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In a sinusoidal electromagnetic wave in a vacuum, the elect field has only an x-component. This component is given by:
Eₓ = Eₘₐₓ cos(ky + ωt).
This wave propagates in the
A. Positive z-direction.
B. Negative z-direction.
C. Positive y-direction.
D. Negative y-direction.
E. Unknown direction.