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The magnetic field of an electromagnetic wave is B = 1.6*10⁻⁶ cos(2*10⁷ z + 6*10¹⁵ t)(2i + j) Wb/m². The associated electric field is:

1. E = 4.8*10² cos(2*10⁷ z + 6*10¹⁵ t)(i - 2j) V/m
2. E = 4.8*10² cos(2*10⁷ z - 6*10¹⁵ t)(2i + j) V/m
3. E = 4.8*10² cos(2*10⁷ z - 6*10¹⁵ t)(-2j + i) V/m
4. E = 4.8*10² cos(2*10⁷ z + 6*10¹⁵ t)(-i + 2j) V/m

Correct answer: E = 4.8*10² cos(2*10⁷ z + 6*10¹⁵ t)(i - 2j) V/m

Solution

E0 = c*B0 = 480 = 4.8*10² V/m. E is perpendicular to B (and to propagation) with the same cosine phase. (i - 2j) is perpendicular to (2i + j), giving option A.

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