Answer: Oscillating or accelerating electric charges.
- A Oscillating or accelerating electric charges
- B Stationary charges sitting at rest in a fixed electric field
- C Constant, unchanging magnetic fields with no time variation
- D Moving uncharged particles such as neutrons or neutrinos
Correct answer: A. Oscillating or accelerating electric charges
Explanation: Accelerating or oscillating electric charges create changing electric fields, which create changing magnetic fields, which in turn create changing electric fields - resulting in EM waves that propagate outward.
In an electromagnetic wave, the oscillating electric field (E) and magnetic field (B) are perpendicular to each other and to the direction the wave travels - a purely transverse wave that needs no medium, unlike sound.
Concept context
Maxwell's equations, EM spectrum, properties, and applications of each band.