Question

Cell phones depend on both mechanical and electromagnetic waves to be useful. Which answer below correctly identifies how each wave is used in cell phones?

Mechanical waves allow the buttons to be pressed to make a call; Electromagnetic waves allow a signal to be picked up when making a call


Mechanical waves light up the screen; Electromagnetic waves create the sound when the phone is ringing


Mechanical waves allow the cell phone to emit a sound when ringing; Electromagnetic waves allow a signal to be picked up when making a call.


Mechanical waves allow a signal to be picked up when making a call; Electromagnetic waves allow the cell phone to emit a sound when ringing

Answer 1

Sound is a mechanical wave. So mechanical waves allow the phone to emit a sound when it rings.

The signal sent out to make a call, and the signal picked up to receive a call, are electromagnetic waves. You also have the electromagnetic waves (called "light") that come pouring out of the screen, so that you can see the stuff on it.

The third paragraph is the correct choice.