1. The Energy of Waves Chapter 20
Section 1
The Nature of Waves pp

2. TERMS TO LEARN
wave – any disturbance that transmits energy through matter or space
Medium – a substance through which a wave can travel

3. TERMS TO LEARN
Transverse wave – a wave in which particles vibrate with an up and down motion
Longitudinal wave – a wave in which particles vibrate back and forth along the path that the wave travels

4. WAVES CARRY ENERGY
Energy can be carried away from its source by a wave, but the material through which the wave travels (i.e. water) does not move with the wave.
Waves carry energy but not matter.

5. WAVES CARRY ENERGY Some waves need a medium to travel through.
These waves are called mechanical waves.
A medium is a substance through which a wave can travel.

6. MECHANICAL WAVES Examples of mechanical waves:
Ocean waves – the medium through which they travel is water
Guitar and cello strings – the medium through which they travel is air

7. ELECTROMAGNETIC WAVES
Waves that DO NOT NEED A MEDIUM TO TRAVEL THROUGH are called electromagnetic waves.
An example of an electromagnetic wave is light.

8. ELECTROMAGNETIC WAVES
Although electromagnetic waves do not need a medium to travel through, they may also travel through a medium like air, glass and water.
Electromagnetic waves (a.k.a. E.M. waves) travel fastest through empty space ( a vacuum).

9. CLASSIFICATION OF WAVES
Waves are classified based on the direction in which the particles vibrate compared with the direction in which the waves move.
The two main types of waves are transverse waves and longitudinal waves.
Longitudinal waves are also called compression waves.

10. TRANSVERSE WAVES
Waves in which the particles vibrate with an up and down motion are called transverse waves.
The particles in a transverse wave move perpendicular to the direction that the wave is traveling.
Example of a transverse wave: a wave moving on a rope.

11. TRANSVERSE WAVE Highest part of wave = crest
Lowest part of wave = trough

12. TRANSVERSE WAVE

13. LONGITUDINAL WAVE
A wave in which the particles move back and forth along the path in which the wave travels is called a longitudinal wave.
Compression – section of a longitudinal wave where the particles are crowded together
Rarefaction – section of a longitudinal wave where the particles are less crowded

14. LONGITUDINAL WAVE

15. LONGITUDINAL WAVE
compression
rarefaction

16. SURFACE WAVES
When waves occur at or near the boundary between two media, a transverse wave and a longitudinal wave can combine to form a surface wave.