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The plan:
Video Clip of the dayVideo Clip of the dayhttp://http://www.youtube.com/watch?vwww.youtube.com/watch?v==
WMPMzhglGooWMPMzhglGoo Introduction to waves Introduction to waves Ways to transmit & transfer energyWays to transmit & transfer energy Wave interferenceWave interference
There are two ways to transmit information/energy in our universe:
1) Particle Motion
2) Wave Motion
Simple Harmonic Motion:
Any motion that repeats itself precisely Any motion that repeats itself precisely over equal periods of time when generated over equal periods of time when generated by a linear restoring force in accordance to by a linear restoring force in accordance to Hooke’s LawHooke’s Law. .
2. WAVE DESCRIPTION
Frequency ( f ) is the number of vibrations per
unit of time made by the vibrating source.
Units - cycles per second
1/s
Hertz (Hz)
Picture of a Transverse Wave
CrestCrest
TroughTrough
WavelengthWavelength
AA
A - AmplitudeA - Amplitude
Distance between adjacent crests in a
transverse wave.
Distance a wave travels during one vibration.
in meters
Wavelength ()
The period (T) of a vibration is the time
required to make one vibration.
The The period (T) of a wave is the time (T) of a wave is the time
required to generate one wave. required to generate one wave.
It is also the time required for the wave to It is also the time required for the wave to
travel one wavelength. travel one wavelength.
FrequencyFrequency PeriodPeriod
ionsec/vibrat21
ionsec/vibrat31
ionsec/vibrat41
ionsec/vibrat2
ionsec/vibrat1
/secvibrations3
secvibration/1
/secvibrations4
ecsvibration21 /
/secvibrations2
FrequencyPeriod
1
Example Question: A mass suspended from the end of a spring A mass suspended from the end of a spring
vibrates up and down 24 times in 36 vibrates up and down 24 times in 36 seconds. What is the frequency and period seconds. What is the frequency and period of the vibration? of the vibration?
Example Question: A mass suspended from the end of a spring A mass suspended from the end of a spring
vibrates up and down 24 times in 36 vibrates up and down 24 times in 36 seconds. What is the frequency and period seconds. What is the frequency and period of the vibration? of the vibration?
Wave Characteristics:
http://www.brightstorm.com/scienchttp://www.brightstorm.com/science/physics/vibration-and-waves/wave/physics/vibration-and-waves/wave-characteristics/e-characteristics/
3. WAVE MOTION
Energy is transported by particles or waves.
A wave is a disturbance transmitted through
a medium.
Exception: light does not require a medium.
For a wave, if the distance traveled is a For a wave, if the distance traveled is a
wavelengthwavelength ( (), then the time to travel this ), then the time to travel this
distance is the distance is the periodperiod (T). Then (T). Then
Tv
fv oror
is true for all waves.
Note: v is dictated by the medium.
(must change medium to change v)
f is dictated by the source.
(must change the source to change f )
Demo - Complete Bell Wave MachineDemo - Complete Bell Wave Machine
fv
5. TRANSVERSE WAVES
Demonstration: Transverse WavesDemonstration: Transverse Waves
Examples: string musical instruments
ripples on water
electromagnetic waves
6. LONGITUDINAL WAVES
Video - Slinky Longitudinal WavesVideo - Slinky Longitudinal Waves
Parameters
Rarefactions are regions of low density.
Compressions (condensations) are regions of high density.
is the distance between successive rarefactions or successive compressions.
7. INTERFERENCE
Video - Superposition of WavesVideo - Superposition of Waves
SlideSlide - Interference - Interference
Constructive interference occurs when waves are in phase, that is when crests are superimposed and troughs are superimposed.
Destructive interference occurs when waves are out of phase, that is when crests are superimposed with troughs.
Standing Waves
When two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still.” It is a changing interference pattern.
Demo - Rope and strobeDemo - Rope and strobe Demo - Mechanical overhead modelDemo - Mechanical overhead model
There is no vibration at a node. There is maximum vibration at an antinode. is twice the distance between successive
nodes or successive antinodes.