Characteristics of Waves

1
Characteristics of Waves

• Chapter 15, pages 472-492

2
What are Waves?

• A wave is a disturbance that transfers energy
  from place to place
• Waves travel through a material called a medium.
• Waves that require a medium to travel through are
  called mechanical waves.

3
What are Waves?

• Waves are created when a source of energy causes
  a medium to vibrate.
• A vibration is a repeated back-and-forth or
  up-and down motion.

4
Classification of Waves

• Wave are classified according to how they move.
• Types of waves
• 1. Transverse
• 2. Longitudinal
• 3. Surface

5
Transverse Wave

• In transverse waves, the particles of the medium
  move perpendicular in the direction of the wave.
• Parts of the transverse wave
• Crest
• Trough
• Wavelength
• Amplitude

6
Longitudinal Wave

• In longitudinal waves, the particles of the wave
  move parallel to direction of the wave movement.
• Parts of the wave
• Compressions
• Rarefactions
• Wavelength

7
Surface Wave

• Surface waves occur at the boundary between two
  mediums and are a combination of transverse and
  longitudinal waves.

8
A transverse wave..

1. Vibrates particles perpendicular to the direction
   of wave
2. Vibrates particles parallel to the direction of
   the wave
3. Vibrates both parallel and perpendicular to the
   direction of the wave
4. Vibrates particles in one direction
5. I dont get it.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23
9
Properties of Waves

• The basic properties of waves are amplitude,
  wavelength, frequency, and speed.

10
Amplitude

• Amplitude is the maximum distance the particles
  of the medium carrying the wave move away from
  their rest position.
• Measured from crest to resting position.

11
Wavelength

• Wavelength is the distance between corresponding
  parts of a wave.
• Wavelength is measured from crest to crest.

12
Frequency

• Frequency of a wave is the number of complete
  waves that pass a given point in a certain amount
  of time.
• Frequency is measured in hertz.

13
Wave Speed

• Wave speed is how far the wave travels in one
  unit of time, or distance divided by time.

14
Mathematical Relationship

• The speed, wavelength, and frequency of a wave
  are related to each other by a mathematical
  formula
• Speedwavelength x frequency

15
In the diagram, identify the wave property A

1. Frequency
2. Amplitude
3. Wavelength
4. I dont know

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23
16
Interaction of Waves

• When waves interact, three things can happen to
  the waves
• Reflect
• Refract
• Diffract

17
Reflection

• Reflection happens when waves bounce off of a
  barrier.
• The angle of incidence is the angle between the
  incoming wave and the imaginary perpendicular
  line.
• The angle of reflection is the angle between the
  reflected wave and the imaginary perpendicular
  line.

18
Law of Reflection

• The angle of reflection is equal to the angle of
  incidence.

19
Refraction

• Refraction occurs as the wave go between
  different mediums.
• The speed of a wave changes as the medium
  changes.
• The change in speed of the wave causes the waves
  to bend.

20
Diffraction

• Diffraction is the bending of waves as the waves
  go through a small opening or around a corner.
• As the wave goes through the hole or around the
  corner, it spreads out and bends.

21
Interference

• Interference occurs as two or more waves
  interact.
• Constructive interference happens when waves meet
  and the amplitude increases.
• Destructive interference happens when waves meet
  and the amplitude decreases.

22
Standing Waves

• Standing waves form as the original wave is
  interfered with by the reflected wave.
• The standing wave has a node and an antinode.

23
Review Questions

• What do we call the transfer of energy from place
  to place?
• (wave)
• What do we call the material through which waves
  travel?
• (medium)
• When the medium _______________, a wave is
  created.
• (vibrate)
• How are waves classified?
• (how they move)

24
Review Questions

• The highest part of a transverse wave is called
  the _______________.
• (crest)
• The lowest part of a transverse wave is called
  the _______________.
• (trough)
• What type of wave travels parallel to the
  direction of the wave travel?
• (longitudinal)
• What type of wave travels perpendicular to the
  direction of the wave travel?
• (transverse)

25
Review Questions

• What type of waves is on top of a pond or lake?
• (surface)
• What property of a wave is the maximum distance
  that particles of the medium move from resting
  position?
• (amplitude)
• What do we call the distance between two
  corresponding parts of a wave?
• (wavelength)
• In what units is frequency measured?
• (hertz)

26
Review Questions

• What is the mathematical relationship between
  speed of a wave, frequency and wavelength?
• (speed wavelength x frequency)
• When a wave hits a barrier and bounces back, it
  is called _______________.
• (reflection)
• When a wave bends because it changes speed as it
  travels through different mediums, it is called
  _______________.
• (refraction)
• When a wave bends as it travels around the edge
  of a barrier it is called _______________.
• (diffraction)

27
Review Questions

• The interaction between two waves is called
  ________________.
• (interference)
• Waves combine to make a wave of larger amplitude
  is called ______________.
• (constructive interference)
• Waves combine to make a wave of lower or no
  amplitude is called _______________.
• (destructive interference)
• What type of wave are two waves that interfere
  with each other as they pass each other?
• (standing)

28
Review Questions

• What occurs when the vibration matches the
  natural frequency of the object?
• (resonance)
• What are the highest and lowest points called on
  a standing wave?
• (antinodes)
• What are the points of zero amplitude called on a
  standing wave?
• (nodes)
• What type of waves does an earthquake produce?
• (seismic)

29
Review Questions

• Longitudinal seismic waves are called
  _______________.
• (primary)
• Transverse seismic waves are called
  _______________.
• (secondary)
• Which type of seismic wave causes the most
  damage?
• (surface)
• Which seismic wave is the fastest?
• (primary)

30
Review Questions

• What type of waves requires a medium to pass
  through?
• (mechanical)
• What name is given to the waves produce by
  underwater earthquakes?
• (tsunamis)
• What machine measures ground movement?
• (seismograph)
• What scale is used to measure the magnitude of
  seismic waves?
• (Richter)

31
Review Questions

• What are the areas of a longitudinal wave where
  the waves are close together?
• (compressions)
• What are the areas of a longitudinal wave where
  the waves are far apart?
• (rarefactions)
• What is the angle defined by an incoming wave and
  the imaginary perpendicular line?
• (angle of incidence)
• What is the angle defined by a reflected wave and
  the imaginary perpendicular line?
• (angle of reflection)

32
Review Questions

• What is the relationship between the angle of
  incidence and the angle of reflection?
• (they are equal to each other)