MLA Citation: Bloomfield, Louis A. "Question 295"
How Everything Works 25 Apr 2018. 25 Apr 2018 <http://howeverythingworks.org/print1.php?QNum=295>.
295. Why do radio waves travel better at night?
AM radio waves travel remarkably long distances near dusk because of the behavior of the earth's atmosphere. A layer in the upper atmosphere, the ionosphere, contains many electrically charged particles and it behaves like a poor electrical conductor. Its conductivity improves in the early evening. When low frequency radio waves encounter this conducting layer, it responds to them and reflects them just like a mirror reflects light. As a result, you can hear very distant radio stations as their waves bounce of the ionosphere. FM transmissions occur at high frequencies that are too fast for the ionosphere to reflect.

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