CBSE Class 12 · 2011 · EM WavesVery Short Answer

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A plane electromagnetic wave travels in vacuum along the z-direction. What can you say about the directions of the electric and magnetic field vectors?

Solution

An electromagnetic wave is transverse, so the field vectors are perpendicular to the direction of propagation.
For propagation along z, both

E

and

B

oscillate in the x--y plane; conventionally

E

along x and

B

along y, so that

E \times B

points along z.

E, B in the x-y plane, mutually perpendicular

CBSE Class 12 Board · 2011 · Subjective

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