Practice portal › Electromagnetic Waves › E and B in the Wave
Asked in GUJCET 2023 · Direction from E cross B, and oblique propagation
Idea: in a plane electromagnetic wave the electric field, the magnetic field and the direction of travel form a right-handed set, taken in that order.
So the wave advances along ⃗E × ⃗B, which is also the direction of the energy flow.
Check it on a wave going along +x with ⃗E along ̂j: then ⃗B lies along ̂k, and ̂j × ̂k = ̂i, which points along +x as it should.
So the direction of propagation is along ⃗E × ⃗B.
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