1. Chapter 4.1 Properties of Waves

2. What are some types of waves?
Microwaves
Waves of water
Light waves
Sound waves
←Maybe not this one…

3. Some important terms…
A wave is a disturbance or movement that transfers energy through space or through matter
Ex: sound waves transfer energy through space (air)
Energy is the capacity to apply force over a distance
A force is a PUSH or a PULL on an object

4. Quick check
What is a force?
What is energy?
What is a wave?

5. The parts of a wave Let’s look at a wave of water:
The rest position (equilibrium position) is shown by a line.
Where the water would be if still
The highest point is called the crest
The lowest point is called the trough

6. The parts of a wave
The wavelength is measured from crest to crest or trough to trough.
Wavelength is a distance and it is measured in metres.

7. The parts of a wave
Amplitude is the height of a crest or depth of a trough measured from the rest position.
Ex: A big wave with a high crest and low trough has a large amplitude.

8. The parts of a wave
The rise and fall of each wave is called an oscillation or a vibration.
Frequency is the number of repetitive oscillations that happen in a given time.
It is usually measured in Hertz (Hz) or cycles per second.

9. Quick check What is the difference between a crest and a trough?
What are 3 ways to measure wavelength?
What property of a wave is measured in hertz?

10. Examples of frequency Frequency = cycles / seconds
A pendulum: 24 swings in 6 s
Merry-go-round: 12 revolutions per 2 min
Flashing red light at an intersection:
30 flashes in 0.5min
Heart rate: 18 beats per 20s
Car drive shaft:2000rpm (revolutions per minute)

12. Water Waves Move Energy
A water wave moves energy (not matter or water).
Energy is carried forward by the water wave.
If you are sitting on an inner-tube in the lake, the wave passes underneath you. Neither you or the water moves forward.

13. What do waves travel through?
The matter that waves travel through is called a medium.
Ex: sound waves travel through air
Air is the medium
Ex: ocean waves travel through water
Water is the medium
We will study 2 types of waves that travel through a medium…

14. 2 Types of Waves 1) Transverse Waves 2) Compression Waves
Matter in the medium moves up and down perpendicular to the direction that the wave travels (ex: waving a rope)
2) Compression Waves
Matter in the medium moves back and forth along the same direction that the wave travels (ex: sound waves)

15. Did you know??
Not all waves need a medium…light waves in space can travel through the emptiness of space (there is no matter at all!)
But sound waves DO need a medium to travel through which means there is no sound in space!