Trevor is looking at data from an experiment where electromagnetic and mechanical waves were sent through various media. The movement of the particles in the wave and the behavior of the wave as it moved from air into each medium is shown in a table.
Wave Movement of Particles Behavior in Water Behavior in Vacuum
1 right and left slowed down sped up
2 front and back sped up no motion
3 front and back sped up no motion
4 up and down sped up no motion
5 right and left slowed down sped up

Trevor would like to determine which waves in the experiment were electromagnetic and which of the waves were mechanical. Which question should Trevor ask to help categorize the waves correctly?

A
What type of wave can travel through water?

B
What type of wave travels at the fastest speed?

C
What type of wave cannot travel through a vacuum?

D
What type of wave can change speed and direction?

- Mechanical waves: these waves are produced by the oscillations of the particles in a medium. By definition, therefore, these waves need a medium in order to propagate. Examples of mechanical waves are sound waves.

- Electromagnetic waves: these waves consist of oscillations of the electric and magnetic fields that propagate in space. Contrary to mechanical waves, these waves do not need a medium to propagate, therefore they can travel in a vacuum. Examples of electromagnetic waves are light waves.

From the definitions above, it is clear that mechanical waves cannot travel through a vacuum, while electromagnetic waves can. Therefore, the correct question that allows to categorize the waves is

C What type of wave cannot travel through a vacuum?