What actually generates electromagnetic radiation in the first place?
AA stationary electric charge sitting at rest in space
BA magnetic material that carries no current at all
CA moving electric charge, that is, an electric current
DA neutral object with balanced positive and negative charge
Answer & Solution
Correct answer: C. A moving electric charge, that is, an electric current
1. Electromagnetic radiation is generated by a moving electric charge, which is the same thing as an electric current.
2. A charge that sits perfectly still cannot radiate, because there is no current associated with it.
3. A neutral object has no net charge to move in the first place, so it cannot be the source either.
4. Magnetic materials only radiate if a current is actually flowing through them, so the material alone is not enough.
_Source: OpenStax Physics (CC BY 4.0), Ch 15 "Light", section 15.1 The Electromagnetic Spectrum_
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