Question

Which property describes an electromagnetic wave and not a mechanical wave?
A. Travels in a vacuum
B. Transfer energy
C. Has frequency
D. Requires a medium

Answer 1

A
Although EM waves do NOT REQUIRE a medium, the charming souls can still travel through mediums - you can see through glass windows.
The classic demo of this is the BELL JAR demo. Electric bell inside a jar which, unfortunately, is called a bell jar 'cos it's shaped like a bell (ugh). Air is pumped out with a pump (!). The electric bell can't be heard - mechanical waves - but you can still SEE the actual bell.
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