MAKING WAVES
PHYSICS IS PHUN – January 2007
S“Please be seated”
Welcome and Thanks
STonight: Properties of waves with application to sound and light
S1. How to view slide show from the web
2. Web pages of interest to pre-college students
SPerhaps the most important wave demonstration
DH1-01: BELL IN VACUUM
Tell story of apparatus.
Athanasius Kircher (1650), Robert Boyle (1660)
TRANSVERSE WAVES
STransverse Waves
DG3-28: SUSPENDED SLINKY
DM7-05: ROPE AND COOKIE COOLERS
DM7-03: POLAROIDS AND GOOSENECK LAMP
DK8-01: ELECTROMAGNETIC WAVE – MODEL
Sc = f
SSpeed of light
SElectromagnetic Spectrum
LONGITUDINAL WAVES
SLongitudinal Waves
DG3-28: SUSPENDED SLINKY
DH1-02: SPEAKER AND CANDLE (use flex-cam with lazy susan for speaker/candle)
Ss = f
SSpeed of sound
S“Sonic” Spectrum
Eg: Band’s bass/treble sounds arrive simultaneously at back of hall
SComparison of transverse and longitudinal waves
(page 2)
PROPERTIES OF WAVES
SWave Properties I
1. Superposition
SB&S Superposition
Comment: Infinite number of waves can exist at the same point at the same time.
Do not affect each other.
DG3-28 SUSPENDED SLINKY
Transverse standing waves
Longitudinal standing waves
2. Huygens’s Principle
SB&S Huygens’s Principle
Comment: Diffraction arises from Huygens’s principle
3. Doppler Effect
SDoppler Effect
DH2-41: DOPPLER BALL
DH1-51 AUDIOTAPE 42 MIN - SCIENCE OF SOUND - SHORT VERSION
Doppler effect with racing cars section
SSolar Fraunhofer spectrum
Comment: Doppler shift of spectrum gives velocities in expanding universe
SWave Properties II
4. Diffraction
SB&S Diffraction
VRipple Tank Diffraction segment
Comment: Long wavelength diffracts more than short wavelength
DLASER BEAM SHINING ACROSS LECTURE HALL – use white card & walk
Comment: Light casts shadows
DM1-02: LASER DIFFRACTION - VARIABLE SINGLE SLIT
DH2-31: ACOUSTIC COLLIMATOR
Comments: Voices muffled around corners
Marching band low instruments heard before high instruments around corner
SSound barriers along highways – limited effectiveness due to diffraction
(page 3)
5. Interference
SInterference
Sound Examples:
DH2-21: AUDIBLE YOUNG'S EXPERIMENT - GROUP LISTENING
DH2-27: PHASE REVERSAL BETWEEN STEREO SPEAKERS - OSCILLATOR
DH2-26: PHASE REVERSAL BETWEEN STEREO SPEAKERS
DH2-32: SPEAKER WITH BAFFLE
SComment: Commercial applications eg. Industrial noise cancellation and
Electronic car muffler
SLight Examples:
DM1-11: LASER DIFFRACTION - FIXED DOUBLE SLITS
DM4-25: INTERFERENCE IN LARGE SOAP FILM - SODIUM AND WHITE
Comment: Natural colors/dyes broad-band, unsaturated, eg dyed clothing
Interference colors narrow-band, saturated, brilliant, eg peacock feather
SPeacock feather
Comment: Interference colors called “iridescence”
6. Reflection
SReflection --- Mirrors light) and echoes (sound)
DL3-24: OPTICAL BOARD - SPHERICAL AND PARABOLIC MIRRORS
DL3-18: FOCUSING OF HEAT WAVES - OVERHEAD PROJECTOR
DH2-02: PARABOLIC MICROPHONE
Examples: Telescope mirror, searchlight, whispering chamber, microwave dish
DH2-33: SPEAKER AND EXPONENTIAL HORN
DL5-01: OPTICAL BOARD - TOTAL INTERNAL REFLECTION
DL5-13: PLEXIGLASS SPIRAL WITH LASER
DL5-24 FIBER OPTICS - COMMUNICATION LINE
7. Refraction
SRefraction
DL4-01: OPTICAL BOARD - RECTANGULAR SLAB
DL6-03: OPTICAL BOARD - HYPERBOLIC LENS
DH2-11: SOUND LENS
SWaves approach parallel to beach
SMirage Schema
DL4-22: MIRAGE - LASER AND HOT WIRE
SWater Mirage
SMirages
DM7-31: TYNDALL'S EXPERIMENT - COLLOIDAL SUNSET
S2 Sunset Photographs
SBye-bye
Pre-Show Demonstrations
Ultrasound
H1-41: ULTRASONIC MOTION DETECTOR
H2-42: ULTRASONIC PEST CONTROLLER
Polarization
M7-01: MICROWAVES - POLARIZATION
M7-17: REFLECTION OF LIGHT FROM DIELECTRIC AND CONDUCTOR
M7-07: CROSSED POLAROIDS - E FIELD COMPONENTS
Extra sheets of polarizing sheet
L3-16: FOCUSING OF HEAT WAVES BY MIRRORS
G3-43: WHIP
G4-22: CHLADNI FIGURES - OSCILLATOR DRIVEN
Laser with single slit slide, double slit slide, and grating slides
K8-04 SPEED OF LIGHT
G4-41 SOLITONS
H3-01 STANDING SOUND WAVES - TWO SOURCES
N1-01 PRISMATIC SPECTRUM OF WHITE LIGHT - POINT SOURCE