Answer:17: A wave can be defined as follows: It is important to realize that a wave is quite a different object than a particle. A baseball thrown though a window transfers energy from one point to another, but this involves the movement of a material object between two points.
Step-by-step explanation:
18: In this way, we classify waves into electromagnetic and mechanical waves. The main difference between mechanical and electromagnetic waves is that electromagnetic waves do not require a medium to propagate whereas mechanical waves require a medium in order to propagate.