http://www.youtube.com/watch?v=yVkdfJ9PkRQ (Pendulum)

1

• http//www.youtube.com/watch?vyVkdfJ9PkRQ
  (Pendulum)

2
Waves

• Most information reaches us as a form of wave.
• Light (electromagnetic), sound, radio/television
  (electromagnetic)
• When energy is transferred by a wave from a
  vibrating source to a receiver, there is no
  transfer of matter between the two points.
• When you cause a ripple in a pond, the wave
  disturbance moves, not the water when the ripple
  passes,the water is in the same spot as it was
  prior to the disturbance.
• The energy transferred from a vibrating source to
  a receiver is carried by a disturbance in a
  medium.
• When you speak, the air molecules dont move away
  from you like a wind they simply pass on the
  disturbance.

3
Great Sound demos on Sound disc!!!!!

• http//www.youtube.com/watch?v44kdfyN9ws4NR1
  (water balloon ping pong ball)

4
Vibrations and Waves

• A wave is a disturbance that carries energy thru
  matter or space.
• A vibration provides the energy for waves - the
  bigger the vibration, the bigger the wave.
• A vibration cannot exist in one instant, but
  needs time to move to and fro.
• A wiggle in time
• As waves carry energy along, they spread that
  energy over a large area - the farther away you
  are from the vibration, the less you are affected
  by it.
• Ex Homes near an epicenter (source of
  vibration) of an Earthquake, versus far away
• The farther you are from a light source, the
  dimmer the light that reaches you.

5
Vibrations and Waves

• Waves that move thru space are called
  electromagnetic waves - their energy is carried
  thru changing electric and magnetic waves.
• Ex Light and heat travel from the sun thru
  space

6
Vibrations and Waves

• All other waves are mechanical waves, which must
  travel thru some form of matter, called a medium,
  in order to move their energy from one location
  to another.
• Ex Earthquakes - energy moves thru the ground
• NOTE The wave moves, but NOT THE MEDIUM!!!!!!!!
• There are three main categories of mechanical
  waves, but all three share some important
  characteristics.

7
Transverse Waves

• Whenever the motion of the medium is at right
  angles to the direction the wave travels, the
  wave is a transverse wave.
• Shaking a rope up and down - rope moves at right
  angles to the direction of the wave (along length
  of the rope).
• Waves caused by the stretched strings of musical
  instruments are transverse.
• iPhone in a guitar!
• http//m.youtube.com/watch?vINqfM1kdfUc

8
Longitudinal Waves

• When the particles of the medium move along the
  direction of the wave, and not at right angles to
  it, it is a longitudinal wave or compression
  wave.
• The particles are alternately squeezed together,
  compressions and pulled apart, rarefactions These
  compressions and rarefactions travel along the
  medium.

9

• Rubens Tube
• http//www.youtube.com/watch?vhip-4KF6z4o
• http//youtu.be/hip-4KF6z4o
• http//youtu.be/hip-4KF6z4o
• http//youtu.be/gpCquUWqaYw

• Pyroboard 2d rubens tube
• http//www.youtube.com/watch?v2awbKQ2DLRE

10
Surface Waves

• A surface wave is a wave that travels along a
  surface separating two media.
• Ex Ocean wave - Travels along the surface of the
  water where it meets the air.
• As the wave goes by, anything in its path will
  move up and down as it passes, but also forward
  and backward, combining to make the object move
  in a circle.
• The entire column of water is moving
• Matter is not transported in this type of wave in
  open water, but as waves approach shore, friction
  between the shore and water slows the bottom of
  the wave down and the top falls over it, causing
  anything that was in the column to move toward
  the shoreline, like a toppling building. (ESSAY
  QUESTION!!!!!)

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Parts of a Wave

• Crests
• High points in a transverse or surface wave
• Compressions in a longitudinal wave
• Troughs
• Low points in transverse or surface waves
• Rarefactions in longitudinal waves
• The midline is a straight line drawn thru the
  crests and troughs that represents the middle of
  the wavethis is equilibrium.

www.bbc.co.uk
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Parts of a Wave

• The amplitude of a wave is the distance from the
  midline to the crest (or to the trough) of the
  wave. Thus, the amplitude is the maximum
  displacement from equilibrium.
• In a longitudinal wave, it is the distance from
  the rest area to the area of greatest compression
  or rarefaction.

• The greater the energy of a wave, the greater
  its amplitude.

Amplitude.pngwww.gwenio.com
13
Parts of a Wave

• Any motion that occurs over and over at regular
  intervals is called periodic motion.
• The period is the time required for one cycle
  from start and back again to complete.
• Ex Pendulum swing from the time you let it go
  until it comes back to your hand.
• Ex From the crest of one wave to the crest of
  the next.

Period
science-class.net
14
Parts of a Wave

• Frequency is how many waves pass by in a set
  period of time, .measured in cycles per second
  or hertz (Hz) - Heinrich Hertz demonstrated radio
  waves in 1886.
• The frequency of a wave is equal to the frequency
  of the vibration that causes it.
• One vibration per second is 1 Hz 2 is 2 Hz.
• Higher frequencies are measured in kilohertz
  (kHz) or megahertz (MHz)AM radio waves are
  broadcast in kilohertz and FM are broadcast in
  megahertz.
• A station transmitting at 101 MHz on the FM dial,
  broadcasts radio waves with a frequency of 101
  000 000 Hz. This is the frequency at which the
  electrons must vibrate in the antenna of the
  radio stations transmitting tower. If your car
  stereo is set at 101FM, then its antenna is also
  vibrating at 101 000 000 Hz and picks up the
  signal.

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Parts of a Wave

• If you look at the definitions, period and
  frequency are the inverse of one another
• The longer the period, the smaller the wave
  frequency.
• The greater the frequency, the shorter the period
  must be.
• Frequency 1/period.Period 1/frequency
• If an objects frequency is 2 Hz (2 vibrations
  per sec), its period (time needed to complete one
  vibration) is 1/2 sec
• If an objects frequency is 3 Hz, its period is
  1/3 sec

16
Parts of a Wave

• The wavelength of a wave is the distance from the
  top of one crest to the top of the next (or
  between any successive, identical parts of a
  wave).
• Wavelengths on a beach are measured in meters in
  a pond in cm, and of light in micrometers.
• Wave speed can be found by
  
• Wave speed wavelength (?) / period (T)
  
  how long the wave is / how long it take
  to go by ORWave speed wavelength (?) x
  frequency (f) how long the wave is
  how many in a second
• Increasing the frequency of a wave will decrease
  its wavelength.

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Wave speed (v) wavelength (?) / period (T)

how long the wave is / how long it take
to go by ORWave speed (v) wavelength (?) x
frequency (f) how long the wave is
/ how many in a second

• A wave on a rope has a wavelength of 2.0 m and a
  frequency of 2.0 Hz. What is the speed of the
  wave?
• A motorboat is tied to a dock with its motor
  running. The spinning propeller makes a surface
  wave in the water with a frequency of 4 Hz and a
  wavelength of 0.1m. What is the speed of the
  wave?
• What is the speed of a wave in a spring if it has
  a wavelength of 10cm and a period of 0.2s?
• What is the wavelength of an earthquake wave if
  it has a speed of 5km/s and a frequency of 10 Hz?

18
Wave speed (v) wavelength (?) / period (T)

how long the wave is / how long it take
to go by ORWave speed (v) wavelength (?) x
frequency (f) how long the wave is
/ how many in a second

• A wave on a rope has a wavelength of 2.0 m and a
  frequency of 2.0 Hz. What is the speed of the
  wave?
• v ____
• ? 2.0 m
• f 2.0 Hz
• V 2.0m x 2.0 1/s 4 m/s

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Wave speed (v) wavelength (?) / period (T)

how long the wave is / how long it take
to go by ORWave speed (v) wavelength (?) x
frequency (f) how long the wave is
/ how many in a second

• A motorboat is tied to a dock with its motor
  running. The spinning propeller makes a surface
  wave in the water with a frequency of 4 Hz and a
  wavelength of 0.1m. What is the speed of the
  wave?
• v ____
• ? 0.1 m
• f 4 Hz
• V 0.1m x 4 1/s .4m/s

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Wave speed (v) wavelength (?) / period (T)

how long the wave is / how long it take
to go by ORWave speed (v) wavelength (?) x
frequency (f) how long the wave is
/ how many in a second

• What is the speed of a wave in a spring if it has
  a wavelength of 10cm and a period of 0.2s?
• v ___
• ? 10cm
• T 0.2 s
• V 10cm / .2s 50 cm/s

21
Wave speed (v) wavelength (?) / period (T)

how long the wave is / how long it take
to go by ORWave speed (v) wavelength (?) x
frequency (f) how long the wave is
/ how many in a second

• What is the wavelength of an earthquake wave if
  it has a speed of 5km/s and a frequency of 10 Hz?
• v 5 km/s
• ? ____
• f 10 Hz
• ? v / f 5 km/s / 10 1/s .5 km

22
Vibrations of a Pendulum

• A stone hung from a string is a simple pendulum.
  
• Pendulums swing to and fro with such regularity
  that they have been used to control the motion of
  clocks.
• The time it takes a pendulum to swing thru its
  angle is its period.
• A period depends on the length of the pendulum
  and the acceleration due to gravity. The mass of
  the pendulum does not affect it.
• A long pendulum has a longer period than a short
  pendulum - it swings to and fro more slowly.
• When walking, our legs swing with the help of
  gravity, much like a pendulum like a
  pendulum, a person with longer legs often has a
  slower stride (giraffes horses vs hamsters and
  dachshunds)

23
Mechanical Waves

• The speed of the wave depends on the medium thru
  which it travels.
• Sound waves travel at 330m/s to 350 m/s in air
  and about 4 times that in water.
• Waves travel fastest thru solids, and slowest
  thru gases.why?
• All things being equal, the distance between
  molecules has some effect, but if that was it,
  then all solids would transmit waves well and
  they do not!
• Elasticity! Remember, the molecules need to
  vibrate back and forth so if they are unable to
  spring back, then they cannot carry the impulse
  well. Ex play dough versus steel
• Temperature can affect waves - how?
• Warmer temps equal faster moving particles so
  they pass on energy more quickly..cooler temps
  equal slow moving particles.

24

• 32 out of sync metronomes
• https//www.youtube.com/watch?vkqFc4wriBvEfeatur
  eyoutube_gdata_player
• Or
• http//youtu.be/kqFc4wriBvE

25
Wave Interactions

• A reflection occurs when a wave bounce back when
  it meets an obstacle (wall), or a boundary
  between different media (move from air to water).
  
• The speed and frequency of the wave does not
  change, but it can be flipped upside down.
• Yell into a cave and your words will travel until
  they hit a wall, and then they bounce back at you
  as an echo.
• Other than objects like lamps that emit their own
  light, everything you see is reflecting light
  waves.
• Light waves striking the surfaces of animals,
  houses, etc, reflect back to you, allowing you to
  see them and identify colors. (If its pitch
  black, you cant see anything cuz theres no
  light to be reflected off of the objects.)

26
9GAG - Physics is phun.9gag.com
27
Wave Interactions

• Refraction is the bending of waves when they pass
  from one medium to another, or when the density
  of a medium changes.
• Occurs when one side of a wave moves more slowly
  than the other.
• Studying refraction of underground
  earthquake waves
  have given us
  what we know about the
  Earths
  interior.
• Refraction explains why sound waves travel so
  much more clearly across a body of water at night
  - the cool air above the water refracts the sound
  waves in a downward arc toward the other side of
  the lake...when the air was warmer during the
  day, the same waves would have refracting upward
  and away from someone on the other side of the
  lake.
• Not being able to hear as well across a camp fire

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29
Wave Interactions

• Diffraction is a bending of a wave as it moves
  around an obstacle or through a narrow opening.
• The larger the wavelength compared to the
  obstacle or opening, the greater the diffraction.
• AM radio wavelengths are much larger than FM
• When an AM radio wave reaches an obstacle, it
  bends a great deal spreading the signal out
  over a large width of area.
• FM radio waves can be blocked and lost as you go
  down into a low point in a road, or around a
  large hill.
• The shorter wavelengths give you more definition
  and clarity
• FM stations are clearer and crisper
• Can see eyelashes on an ultrasound

30

• This photo sequence taken in Veszprem, Hungary

As the sun sets toward the horizon, the light has
to travel a longer distance to us and is
scattered more. The shorter wavelengths (blues
and greens) arent as able to get around the
particles in their way and are scattered more,
and the reds and oranges are able to get around
the particles in the way more easily and are the
ones that mostly get to us. - Taken in
Veszprem, Hungary
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Wave Interactions

• An interference pattern occurs when more than one
  vibration is acting in a place at one time,
  causing 2 or more waves to overlap and combine.
• Within a interference pattern, the wave effects
  may be increased, decreased or neutralized.
• Adding the amplitudes of the waves together,
  gives you the resulting wave.

http//youtu.be/PCYv0_qPk-4
http//youtu.be/q74qF6I1uew
33
Wave Interactions

• Constructive Interference When the crest of one
  wave overlaps the crest of another wave, their
  individual effects add together, resulting in a
  wave of increased amplitude.
• Destructive Interference When the crest of a
  wave overlaps the trough of another wave, the
  individual effects are reduced - the high part of
  one wave fills in the low part of the other.
• Can result in neutralization of the wave if the
  amplitudes are the same size.

34
Interference
When the crest of one wave overlaps the crest of
the other, the wave are in phase with each other
and amplify. When the crest of one wave overlaps
the trough of the other, the waves are out of
phase with each other and diminish or cancel out.
35
Wave Interactions

• In a concert hall, you have many sources of sound
  being directed out toward the audience.
• Once the sound leaves the instruments, it may
  travel directly to the listener, but also moves
  out across the entire hall and reflects from
  surfaces around the room.
• If a reflected wave interferes with an original
  wave, they can cancel out and cause dead spots
  where the volume is greatly reduced.
• To avoid this,
• theatres are designed with sound-absorbing tiles
  and reflecting panels to control where the sound
  goes, ensuring it does not double back on itself
  but instead moves toward the audience.

36
Wave Interactions
http//youtu.be/q2AynYYMskA

• Noise-cancellation technology uses interference
  to cancel out unwanted noise.
• Receivers in headsets analyze the amplitude and
  frequency of unwanted sounds, and then a tiny
  speaker emits a wave at the same frequency but
  out of phase so that the two meet and cancel out
  in destructive interference.
• This type of technology distinguishes between
  sounds you do not want and sounds you do so that
  you can hear your coworker talking to you over
  the sound of the jet engine.

37
Standing Waves

• By shaking a rope just right, it is possible to
  cause the incident (original) wave and the
  reflected wave to form a standing wavein a
  standing wave, the nodes are points along the
  rope that remain stationary.
• The positions on a standing wave with the largest
  amplitudes are the antinodes.
• Antinodes occur halfway between the nodes
• Standing waves are the result of interference.
• When two waves of equal amplitude and wavelength
  pass thru each other in opposite directions, the
  waves are always out of phase at the nodes.
• Standing waves can be produced in either
  longitudinal or transverse waves.

38
Standing Waves
Incident Wave
Antinode
Node
Reflected Wave
39

Standing Wave Videos Rubens Tube http//www.yo
utube.com/watch?vynqzeIYA7Iw
http//www.youtube.com/watch?vgpCquUWqaYw
Physics Girl Singing Plates https//www.youtube
.com/watch?vwYoxOJDrZzw or http//youtu.be/wYoxOJ
DrZzw
40
Sound Waves

• Sound waves are mechanical waves and therefore
  follow the same behaviors, with a few additional
  terms specific to sound.
• Intensity is the rate at which a waves energy
  flows through a given area.
• Depends on amplitude and the distance from the
  source.
• Measured in decibels (dB) which is a unit
  developed to compare different sounds.
• The greater the decibel level, the greater the
  intensity and the greater the possible damage
  your ear may receive from that sound. (chart on
  p. 515)
• Loudness is a physical response to intensity.
• Depends on intensity but also the health of your
  ears and how your brain interprets information in
  the sound waves.

41
Wave Characteristics
https//www.youtube.com/watch?vdbeK1fg1Rew
First half on parts of wavelast half on pitch
42
Sound Waves

• Remember, frequency depends on the speed of the
  vibrating source.
• Pitch is the frequency of a sound as you perceive
  it.
• Affected by the waves frequency but again, also
  on age, health, etc.
• The higher the frequency of a wave, the higher
  its pitch.
• Musical Instruments produce standing waves in the
  tubing (trumpet, oboe, pipes), along the strings
  (piano, violin) or across the vibrating surfaces
  (drums) that makes them up Diff in a bass drum
  and snare?
• the longer the tubing, string or larger surface
  area, the longer the wavelength of that standing
  wave that can be created the lower the frequency
  lower pitch.
• Shorter tubing (string, surface area) allows for
  only short standing waves higher frequencies
  and therefore higher pitch.

43

• http//science360.gov/obj/video/7f361151-7757-4083
  -86f4-81899df65bfa/innovation-nation-sound-bullets
  

44
Music

• Most musical instruments change the frequency of
  standing waves to change their pitch.
• Resonance is the response of a standing wave to
  another wave of the same frequency.
• Can produce a dramatic increase in amplitude.
• Soundboard in a piano is a board that resonates
  or vibrates in response to the vibrating strings,
  increasing their amplitude.
• Acoustic guitars use a soundboard (the wooden
  front and back of the guitar) and sound box
  (hollow cavity) - vibrations from the strings
  resonate the soundboard and resonate the air
  inside the sound box, changing amplitude
  depending on how those frequencies align.

45

• http//www.youtube.com/watch?vuENITui5_jUfeature
  youtube_gdata_player

Camera trick Camera is set to 24 Frames per
second
When sound frequency is same, appears still
When sound frequency is at 25Hz, appears to move
slowly forward When sound frequency is at
23Hz, appears to move slowly forward
46
Sound Waves

• Most people hear sounds between 20 Hz and 20,000
  Hz though age affects this a great deal.
• As you age you lose the ends of that spectrum,
  so you can hear much higher and lower sounds than
  your parents can.
• Ultrasound is sound higher than most people hear
  and infrasound is sound at lower frequencies.
• Sonar (sound navigation and ranging) bounces
  sound off of objects in water, and then uses the
  speed of sound in water and the time it takes for
  the echo to return to determine the distance to
  the object and create a 3D map of it.
• Ultrasound imaging is used in the same way on
  much smaller objects, i.e. human organs, fetus in
  the womb, etc.

47
Sound Waves

• A change in frequency relative to motion of the
  source or receiver or both is called the Doppler
  effect.
• The greater the speed of the source (or
  receiver) the greater the Doppler effect.
• The wave crests in front of a moving source of
  light or sound are closer together than those
  behind it, so the receiver would experience a
  higher frequency if he is in front of the source.
• Changing pitch of a car horn as it passes by - as
  it approaches, its pitch is higher because its
  sound wave crests are reaching you more
  frequently as it passes and moves away, the
  pitch drops cuz the waves encounter you less
  frequently.
• http//videos.howstuffworks.com/discovery/27963-as
  signment-discovery-doppler-effect-video.htm

http//www.youtube.com/watch?vLIvVzJ6KZpk
48
The Doppler Effect

• Light waves also experience the Doppler
  effect.as a light source approaches, there is an
  increase in frequency and as it recedes, there is
  a decrease in frequency
• An increase in light frequency is called a blue
  shift, as the increase is toward the
  high-frequency, or blue, end of the color
  spectrum.
• A decrease in frequency is called a red shift,
  referring to the low-frequency, or red, end of
  the color spectrum.
• When scientists look at the universe they see a
  trend toward a red shift, which indicates that
  the expansion of the universe is slowing,
  supporting the Big Bang theory.

49
Sound Waves

• When the speed of the source is the same as the
  speed of the waves it produces, a wave barrier
  is produced.
• When a wave barrier is produced, the crests keep
  piling up in front of the source in order for
  the source to pass this barrier and go faster, it
  must exert a great deal of energy.
• When aircraft fly at the speed of sound, a
  barrier of compressed air is produced in front of
  the plane. Additional thrust is required to
  burst through.
• The sudden increase in pressure can cause the
  water vapor in the air to condense into visible
  water droplets or clouds.

The PrandtlGlauert Singularity Amazing Jet
Plane Shock Collar ...www.kuriositas.com
Ares I-X Launch Image Gallerywww.universetoday.com
50
Shock Waves
https//www.youtube.com/watch?vgWGLAAYdbbcfeatur
eyoutube_gdata_player

• A boat speeding thru water faster than the waves
  it is producing, creates a 2 dimensional shock
  wave. An aircraft flying faster than the speed
  of sound (supersonic) produces a 3 dimensional
  shock wave.
• A shock wave is produced by overlapping spheres
  that build up. The conical shock wave spreads
  until it reaches the ground.
• A sonic boom is the sharp crack of noise heard
  when the conical shock wave reaches the listeners
  on the ground.

51
Sound Waves
Which travels faster, sound or light?
This is footage of the meteor that landed in
Russia, early in the morning on February 15,
2013. The damage to the buildings was caused by
SOUND WAVES!
https//www.youtube.com/watch?vpFBtfR54Svk
https//www.youtube.com/watch?v1kvHl5Qcnzc
https//www.youtube.com/watch?vwZ2XXa5oFhw
Volcano Eruption in Papua New Guinea sound
waves, clouds. http//www.youtube.com/watch?vBU
REX8aFbMs
52
Shock Waves

• Only when the craft moves faster than sound do
  the crests overlap, and are encountered by the
  listener as a single burst - the sonic boom.
• This sudden increase in pressure is the same as
  produced by an explosion - the ear cannot
  distinguish between the high pressure from an
  explosion and that from a sonic boom.
• A sonic boom is not produced at the moment the
  aircraft passes thru the sound barrier - it is
  heard when the waves reach the listener.

53
Hearing and Your Ear

• There are three major areas of the ear outer
  ear, middle ear and inner ear
• The outer ear gathers and focuses sound into the
  middle ear.
• Middle ear receives and amplifies the vibrations
• The inner ear organ called the cochlea is filled
  with fluid and nerve endings with tiny hair-like
  projections that sway as the vibrations move thru
  the fluid and send the signals to the brain for
  translation.

54
biology-pictures.blogspot.com