Waves

1

• Waves

2

• Waves are everywhere.
• List some examples of types of waves...

3

• Sound Waves
• Light Waves
• Radio Waves
• Stadium Waves
• Earthquake Waves
• Water Waves

4

• Water Waves
• have a crest and a trough and travel from one
  location to another.
• One crest is followed by a second crest, with a
  trough in between.

5

• Stadium Waves
• a ripple is produced when fans stand up, put
  their arms up, and then sit back down. This
  ripple will travel in a circle around the stadium.

6

• The wave is passed from row to row as each
  individual member of the row becomes temporarily
  displaced out of their seat, only to return to it
  as the wave passes by.

7

• Slinky Waves
• waves will subsequently be seen traveling from
  one end of the slinky
• to the other. As the wave moves along the slinky,
  each individual coil is seen to move out of place
  and then return to its original position.

8

• The coils always move in the same direction that
  the first coil was vibrated. A continued
  vibration of the first coil results in a
  continued back and forth motion of the other
  coils. If looked at closely, one notices that the
  wave does not stop when it reaches the end of the
  slinky rather it seems to bounce off the end and
  head back from where it started.

9

• Wave
• a disturbance that travels through a medium from
  one location to another location.

10

• Equilibrium Position
• Wave is at rest
• Disturbance
• Particle Movement
• Pulse
• Single disturbance moving through a medium from
  one location to another

11

• Medium
• Substance or material that carries the wave.
• Particles of the medium interact with each other
  and transmit the wave.

12

• What is the medium if...
• A choir is singing?
• There is a stadium wave?

13

• When a wave is present in a medium (that is, when
  there is a disturbance moving through a medium),
  the individual particles of the medium are only
  temporarily displaced from their rest position.
  There is always a force acting upon the particles
  which restores them to their original position.

14

• TRUE or FALSE
• In order for John to hear Jill, air molecules
  must move from the lips of Jill to the ears of
  John.
• Alex sends a pulse along a rope. How does the
  position of a point on the rope, before the pulse
  comes, compare to the position after the pulse
  has passed?

15

• In order for a medium to be able to support a
  wave, the particles in the wave must be
• a) frictionless.
• b) isolated from one another.
• c) able to interact.
• d) very light.

16

• Waves can be classified based on some very
  distinctive properties
• Transverse Waves
• Longitudinal Waves
• Surface Waves

17

• Transverse Waves particles of the medium move in
  a direction perpendicular to the direction which
  the wave moves.
• Particle movement is perpendicular to wave
  motion.

18

• Stretch a slinky across the room.
• On one end of the slinky, vibrate the first coil
  up and down (a pulse).
• The energy moves from left to right, and the
  coils are displaced upwards and downwards.

19

• Longitudinal Waves particles of the medium move
  in a direction parallel to the direction which
  the wave moves.
• Particle movement is parallel to wave motion.

20

• Stretch a slinky across the room.
• On one end of the slinky, vibrate the first coil
  left and right (a pulse).
• The energy moves from left to right, and the
  coils are displaced to the left and to the right.

21

• Example of longitudinal waves
• Sound Waves
• Ocean Waves
• (in the depths of the ocean)

22

• Waves in a solid medium can either be transverse
  or longitudinal.
• Waves in a liquid or a gas are always
  longitudinal waves.
• (This is because transverse waves require a rigid
  medium to be transported. If not rigid,
  particles will slide past each other.)

23

• Earthquakes cause both longitudinal and
  transverse waves.
• However, in the core of the earth, there are only
  longitudinal waves.
• This is what has lead geologists to believe that
  the earth has a molten, liquid core.

24

• Surface Waves wave in which particles of the
  medium undergo a circular motion.
• Only the particles on the surface experience
  circular motion.

25

• Example of surface waves
• Ocean Waves
• (on the surface of the ocean)

26

• All waves have a source - a place where the
  disturbance begins.
• Slinky 1st coil
• Sound Wave Vocal Chords
• The particles which are displaced from their
  equilibrium position always moves in the same
  direction as the source of the vibration.

27

• A transverse wave is transporting energy from
  east to west. The particles of the medium will
  move
• a. east to west only
• b. both eastward and westward
• c. north to south only
• d. both northward and southward

28

• A wave is transporting energy from left to right.
  The particles of the medium are moving back and
  forth in a leftward and rightward direction. This
  type of wave is known as a
• a. mechanical
• b. electromagnetic
• c. transverse
• d. longitudinal

29

• The crest of a wave is the point on the medium
  which exhibits the maximum amount of positive or
  upwards displacement from the rest positon.
• The trough of a wave is the point on the medium
  which exhibits the maximum amount of negative or
  downwards displacement from the rest positon.

30

• amplitude of a wave refers to the maximum amount
  of displacement of a a particle on the medium
  from its rest position.
• (distance from rest to crest)

31

• wavelength of a wave is simply the length of one
  complete wave cycle.
• A wave has a repeating pattern. And the length of
  one such repetition (known as a wave cycle) is
  the wavelength. The wavelength can be measured as
  the distance from crest to crest or from trough
  to trough.

32

• The wavelength of the wave in the diagram above
  is given which letter?
• The amplitude of the wave in the diagram above is
  given which letter?

33

• Indicate the interval which represents one full
  wavelength
• a to c
• b to d
• a to g
• c to g

34

• The frequency of a wave refers to how often the
  particles of the medium vibrate when a wave
  passes through the medium.
• units of cycles/second, waves/second,
  vibrations/second, or something/second. Another
  unit for frequency is the Hertz where 1 Hz is
  equivalent to 1 cycle/second.

35

• The period of a wave is the time for a particle
  on a medium to make one complete vibrational
  cycle.
• Frequency refers to how often something happens
  period refers to the time it takes something to
  happen.

36

• A wave has an amplitude of 2 cm and a frequency
  of 12 Hz, and the distance from a crest to the
  nearest trough is measured to be 5 cm. Determine
  the period of such a wave.

37

• A fly flaps its wings back and forth 150 times
  each second. The period of a wing flap is
• a. 150 sec
• b. 2.5 sec
• c. 0.040 sec
• d. 0.0067 sec

38

• A tennis coach paces back and forth along the
  sideline 10 times in 2 minutes. The frequency of
  her pacing is ________.
• a. 5.0 Hz
• b. 0.20 Hz
• c. 0.12 Hz
• d. 0.083 Hz

39

• The frequency of rotation of a second hand on a
  clock is _______.
• a. 1/60 Hz
• b. 1/12 Hz
• c. 1/2 Hz
• d. 1 Hz
• e. 60 Hz

40

• The frequency of rotation of a second hand on a
  clock is _______.
• a. 1/60 Hz
• b. 1/12 Hz
• c. 1/2 Hz
• d. 1 Hz
• e. 60 Hz

41

• The speed of a wave is the distance traveled by a
  given point on the wave (such as a crest) in a
  given period of time.
• Speed distance/time
• Speed Wavelength Frequency
• v f ?