Explanation:
Not all waves actually require a physical medium through which to travel. This fact allows us to put all waves into two broad categories:
Mechanical Wave - A wave that requires a physical medium through which to travel. Example - sound waves. Sound waves can not travel through a vacuum (empty space).
Electromagnetic Waves - Do not require a physical medium through which to travel. Electromagnetic waves can travel through a vacuum. Examples: Radio waves, visible light, x-rays, etc.
