Chapter 4.1 Properties of Waves

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

• Lets 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 shaft2000rpm (revolutions per minute)

11
(No Transcript)
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
• 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 mediumlight 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!