Answer: AM radio broadcasting (long distance, ground and sky waves).
- A AM radio broadcasting (long distance, ground and sky waves)
- B FM radio, which instead relies on direct line-of-sight propagation
- C Optical fiber communication, which uses total internal reflection in glass
- D Satellite TV, which relies on direct transmission through the ionosphere
Correct answer: A. AM radio broadcasting (long distance, ground and sky waves)
Explanation: AM radio uses frequencies (535-1705 kHz) that are reflected by the ionosphere. This allows AM signals to travel beyond the horizon. FM radio (88-108 MHz) passes through the ionosphere and is used for shorter ranges.
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.