1. Chapter 15.1: What are waves?
Key concepts: What causes mechanical waves? What are two types of waves and how are they classified?
Key terms: wave, energy, medium, mechanical wave, vibration, transverse wave, crest, trough, longitudinal wave, compression, rarefaction

2. Waves and energy
A wave is a disturbance that transfers energy from place to place.
Energy is the ability to do work. (again)
Example: a raft

3. Say what now, huh, how is a wave what now?
A wave that disturbs the surface of the water will also disturb the raft
The wave’s energy lifts the heavy raft as the waves passes under it

4. What carries waves?
Most kinds of waves need something to travel through. The material through which a wave travels is called “medium”
Gases, liquids, and air are all considered mediums
Waves that need a medium are called “mechanical” waves
Not all waves require a medium to travel through (more on this later)

5. How do waves transfer energy?
Waves do NOT carry the medium with them.
When a wave enters a medium, it transfers energy to the medium’s particles.
The particles bump into each other and pass the ENERGY along.

6. What causes waves?
Mechanical waves are produced when a source of energy causes a medium to vibrate.
Vibration is a repeated back and forth or up and down movement.
When a vibration occurs through a medium, a wave results.

7. Types of waves
Mechanical waves are classified by how they move. There are two types of mechanical waves:

8. Transverse waves
Transverse – waves that move in a medium at right angles to the direction in which the wave travels
Crest – high part of a transverse wave
Trough – low point of a transverse wave
Example: “the wave” at a sports arena.. The wave moves around, you see it as people popping up and down

9. Longitudinal waves
Move the medium parallel to the direction in which the waves travel
The coils in the spring move back and forth parallel to the wave motion
Compressions – when the coils are close together
Rarefactions – parts where coils are spread out
Examples: A slinky. Sound waves.

11. Representing types of waves
You can represent waves with simple diagrams
Transverse have crests and troughs
Longitudinal have coils
Please look at page 514