I keep getting “Changing fields sustain an electromagnetic wave” questions wrong in Electromagnetic Waves. What's the trap?
saying electromagnetic waves require a material medium.
The usual trap: saying electromagnetic waves require a material medium. How to avoid it: changing E makes B; changing B makes E. Go back to the definition — A changing electric field produces magnetic effects and a changing magnetic field produces an electric field. This coupled disturbance can travel through vacuum without charges continuously carrying it forward.
Key point
Changing fields sustain an electromagnetic wave
Common mistake
saying electromagnetic waves require a material medium.
Memory tip
changing E makes B; changing B makes E.
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