Waves

1
Waves

• Waves are rhythmic disturbances that carry or
  transmit energy through matter and space.
• They may or may not need a medium

2
Medium

• medium, the ____________ through which a wave
  transfers.
• What is the medium in this picture

3
What other mediums are there

• What is this medium

4
Sort of a wave PendulumSimple harmonic motion

• Regular motion
• Period time of the back and forth swing
• Dependent only on the length of the string and
  gravity
• Not dependent on mass

5
T for the period of a pendulum 2 pie times the
square root of the length of the pendulum
divided by gravity or 10 m/s squared
6
Frequency for pendulum
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Mechanical waves need a __________

• Which of the following is a mechanical wave
• radio waves ___________
• sonic booms __________
• earthquakes ___________
• a slinky vibrating ___________
• AC current for your home ______
• magnetism ______________
• light _____________________

8
Sine waves crest and troughs

• The highest __________ of a wave are called the
  ______________
• The lowest the points on a wave are called the
  ___________________

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Amplitude and wavelenght
10

• Wavelength is the ____________________ between a
  point on one wave and the identical point on the
  next wave.
• Amplitude is the ________________________ from
  the crest ( or trough) of a wave to the rest
  _________________________ of the medium

11
Frequency

• Frequency is the number of complete vibrational
  cycles of a medium per a given amount of time.
• It is measure in Hz or Hertz or cycles per second

12
Frequency

• Time is one second
• What is the
• Frequency?
• 6 cycles /s
• 3 cycles/s

13
AM and FM radio

• Kilohertz for AM radios long wave lengths
• FM are broadcast in megahertz.
• Higher frequencies have higher energies
• Gamma rays have the most energy

14
Frequency and periods

• Frequency 1/ period
• Period 1/ frequency

15
Velocity of a wave

• Wave Velocity
• Velocity wavelength times the frequency

16
Sound is a ____________ wave?

• Water waves are a ____________ wave?
• Transverse wave, the medium moves at right angles
  to the ___________ the wave _______________.

17
Transverse waves and Longitudinal waves
18
Sound Waves in air

• Chart on page 377 copy
• The speed is the same at 340 m/s
• Frequency can go from 160 ( we can hear at 20 hz
  to 20,000 hz)
• The speed stays the same as the frequency and
  wavelength vary inversely

19
Harmonic motion and waves

• Waves will have nodes and antinodes
• We can add the amplitude of two waves together.
• http//id.mind.net/zona/mstm/physics/waves/standi
  ngWaves/understandingSWDia1/UnderstandingSWDia1.ht
  ml
• More than one wave http//www.colorado.edu/physics
  /2000/schroedinger/

20
Interference

• May increase, decrease, or cancel and form beats
• Constructive add
• Destructive subtract
• Nodes and standing waves

21
Combining waves

• ___________________ is the ability of two or more
  waves to combine and form a new wave.
  Constructive interference occurs when the
  _____________ of different waves arrive at the
  same ________ at the same ____________
• Destructive interference is ______________________
  _
• The effect produced by many reflections of sound
  is called ______________

22
Standing waves
23
Doppler effect

• An object moving towards the receiving party will
  have a higher pitch or frequency
• Blue shift
• Red shift then the object is moving away or lower
  pitch

24
Doppler effect

• Pitch frequency
• The ___________ the pitch, the higher the
  frequency.
• An observed change in the frequency of a wave
  when the source is moving relative to the
  receiver.
• If the source is coming towards you the pitch
  will __________?

25
Bow waves and sonic boomswaves piling up
26
What causes a drum to work

• How do you talk
• What does vibration have to do with sound
• Three types of waves transverse longitudinal and
  circular

27
Sound waves

• Produced by vibrations of material objects
• Pitch frequency
• Human hearing 20 to 20,000 hertz
• Compress ional or longitudinal wave

28
10-3 combining waves

• ___________ the bouncing back of a wave as it
  meets a surface or boundary

29
Page 380

• ____________ is the bending of a wave as it
  passes an edge or an opening

30
Combining waves

• ___________________ is the ability of two or more
  waves to combine and form a new wave.
  Constructive interference occurs when the
  _____________ of different waves arrive at the
  same ________ at the same ____________
• Destructive interference is ______________________
  _
• The effect produced by many reflections of sound
  is called ______________

31
Reflection

• Waves can and do meet boundaries in their medium.
  When a wave meets a boundary, it can be reflected
  or transmitted. Reflection can be partial or
  complete. Reflection can also involve a phase
  flip (change of phase of 180 degrees.)

32
Reflected and obsorbed
33
Transmitted waves are refracted or diffracted

• Refraction occurs when a wave crosses a boundary
  from one medium to another. A wave entering a
  medium at an angle will change direction.
• Diffraction refers to the "bending of waves
  around an edge" of an object. Diffraction depends
  on the size of the object relative to the
  wavelength of the wave.
• All these phenomena apply to electromagnetic
  waves, such as light waves, as well as to
  pressure waves and water waves.

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Diffracted
35
Refracted wave

• Incident
• wave
• Refracted
• wave

36
Interference in music and light

• Why do bubbles or oil on water have a rainbow of
  color?
• Why do you hear beats?

37
Harmonic motion and waves

• Waves will have nodes and antinodes
• We can add the amplitude of two waves together.
• http//id.mind.net/zona/mstm/physics/waves/standi
  ngWaves/understandingSWDia1/UnderstandingSWDia1.ht
  ml
• More than one wave http//www.colorado.edu/physics
  /2000/schroedinger/

38
Speed depends on the medium

• Travel slower through gasses
• Faster through solids
• Why does the Indian listen to the railroad
  tracks
• Sound must have a medium
• Star Wars was a fake
• Next chart the speed of sound

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Sound loudnesslogarithmic

• Amplitude measured in Decibels (dB)
• Jet engine 140
• Pain 120
• Rock concert 115
• Busy street 70
• Library 40
• Breathing 10

41
Sounding boards and amplification

• Natural frequency objects have their own
  natural frequency
• Depends on elasticity Putty does not vibrate
• Shape is important and size
• Force Vibration and sounding boards
• page 394

42
Resonance page 395

• Resonance occurs when the forced vibration is the
  same as frequency as the natural frequency.
  Increase amplitude
• Constructive interference some places have good
  acoustics meaning constructive interference

43
Interference, acoustics and beats

• Interference does occur in sound. It may be
  constructive (louder) or destructive ( lower
  amplitude)
• Beats alternating between constructive and
  destructive interference p. 398

44
Light

• Waves and we have frequency and wavelength
• Photons light consists of particles massless
  bundles of concentrated electromagnetic energy
• Light is energy emitted by accelerating electric
  charges often electrons in atoms!

45

• All matter absorbs and emits electromagnetic
  radiation in discrete small quantities called
  photons. The energy of a photon (E) varies with
  the frequency of the radiation according toThe
  energy of a photon (E) varies with the frequency
  of the radiation according to - where h is a
  constant known as Planck's constant.

46
Electromagnetic waves

• Does light require a medium

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Visible light is a very small portion of the
electromagnetic spectrum

• http//www.colorado.edu/physics/2000/waves_particl
  es/astrolinks.html
• Other types are ___________
• _________________
• ________________________
• ______________________
• _____________________
• _____________________ etc. Page 408

48
Why is glass not transparent to ultraviolet light

• Natural vibration frequency of the atom electrons
  and nucleus. Energy is held by the atom and
  formed usually into heat.
• For light has a lower frequency and electrons
  vibrate at lower amplitude. The energy of the
  vibrating electrons is reemitted as light with
  some heat loss.

49
Opaque Materials

• Materials that absorb light without remission.
• Why are metals shiny?
• Same reason that they conduct heat and
  electricity. Outer layer of electrons are not
  bound to any particular atom. They have free
  electrons. They can reemit light called
  reflection or shiny materials

50
Light a transverse wave and polarization page 415

• Polarized glasses eliminate horizontal wave
  leaving vertical only
• Shadows and umbra total shadow
• and penumbra partial shadow

51
Color

• Spectrum of colors with lowest frequency being red

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Electromagnetic spectrum
53
Why is the sky blue and sunsets red, and how does
a prism work?

• The reason that the white light changes as it
  passes through the glass is due to the fact that
  the beam of light is bent (refracted) when it
  enters the glass because of its decrease in
  speed. The light that comes out of the other side
  of the prism consists of many rays that come out
  at different angles. The different angles are
  what give each ray a different hue (for more on
  refraction and reflection of light, see
  references).

54
Atomic Spectra

• Every element has its own characteristic color
  when made to emit light. Atoms must be far
  enough apart for no interference occurs in the
  gaseous state.
• Spectroscope can determine the element from its
  spectrum
• See chart on page 438
• http//www.colorado.edu/physics/2000/quantumzone/i
  ndex.html

55
Speed of light

• Electromagnetic waves travel in a vacuum at
  300,000 km /sec
• 7.5 trips around the world in one second
• Does light slow down in different mediums?
• Can we stop light? How

56
Reflection
57
Refraction Snells law
58
Index of refraction

• When light travels from one medium to another, it
  generally bends, or refracts.
• Index of refraction the ratio of the speed of
  light in a vacuum to the speed of light in a
  substance

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• Refraction is the bending of the path of a light
  wave as it passes from one material to another
  material. The refraction occurs at the boundary
  and is caused by a change in the speed of the
  light wave upon crossing the boundary. The
  tendency of a ray of light to bend one direction
  or another is dependent upon whether the light
  wave speeds up or slows down upon crossing the
  boundary.

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Values of index of refraction

• Vacuum 1.0000
• AIR 1.0003
• Ice 1.31
• Water 1.333
• Ethyl Alcohol 1.36
• Plexiglas 1.51
• Crown Glass 1.52
• Diamond 2.417

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Light refracts due to the change of speed in a
new mediumSpeed of light in a vacuum
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