waves a disturbance in a medium that transfers energy and momentum
TRANSCRIPT
![Page 1: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/1.jpg)
Waves
A disturbance in a medium that transfers energy and momentum
![Page 2: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/2.jpg)
To produce a Wave:
• A vibration (disturbance)
• A medium – a substance to travel through.
![Page 3: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/3.jpg)
Examples of Waves
• Sound
• Light
• Water
![Page 4: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/4.jpg)
There are two types of waves
![Page 5: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/5.jpg)
Transverse – the individual wave particles move perpendicular to the velocity of the wave.
Examples:
Electromagnetic waves (light waves, radio waves, microwaves, x-rays)
Wave on a string
![Page 6: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/6.jpg)
Longitudinal – the individual wave particles move parallel to the velocity of the wave.
Examples: Sound Waves
![Page 7: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/7.jpg)
Parts of a wave:
Amplitude
Wavelength
Frequency – The number of wave cycles in 1 second.
Tf
1 Units 1/s = Hertz (Hz)
![Page 8: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/8.jpg)
Wave Interference – The combination of two or more waves.
• Constructive interference – Two waves combine to make a bigger wave.
• Destructive interference – Two waves combine to make a smaller wave.
![Page 9: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/9.jpg)
vTf
T1
fv1
wav
elen
gth
(m)
Period (s)
velocity
wavelength = (velocity)(Period)
fv
wav
elen
gth
(m)
frequency (hz)
![Page 10: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/10.jpg)
The Wave Equation
fv v = velocity of the wave (m/s)
λ = wavelength (m)
f = frequency (1/s = Hz)
![Page 11: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/11.jpg)
Example1: A sound wave has a frequency of 256 Hz. What is the wavelength? The speed of sound is 340m/s.
m
s
sm
f
v
fv
33.11
256
340
![Page 12: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/12.jpg)
Example 2: A radio wave has a frequency of 96.9MHz. What is the wavelength? The speed of light is 3.0 x 108 m/s.
m
s
sm
f
v
fv
1.31
109.96
103
6
8
![Page 13: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/13.jpg)
Standing Waves on a String
The velocity of a wave on the string depends on the mass per length of the string and the tension in the string.
LmF
v Tv = velocity of the wave (m/s)
FT= Tension in the string (N)
m = mass of the string (kg)
L = length of the string (m)
![Page 14: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/14.jpg)
The fundamental frequency 1st Harmonic.
L2
v
f
fv
L
vf
21
L
![Page 15: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/15.jpg)
The fundamental frequency 2nd Harmonic.
L
v
f
fv
L
vf 2
L
![Page 16: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/16.jpg)
The fundamental frequency 3rd Harmonic.
L3
2
v
f
fv
L
vf
L
vf
2
332
3
3
L
![Page 17: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/17.jpg)
The fundamental frequency 4th Harmonic.
2
L
v
f
fv
L
vf
Lv
f
22
4
4
L
![Page 18: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/18.jpg)
The fundamental frequency 5th Harmonic.
L5
2
v
f
fv
L
vf
Lv
f
2
552
5
5
L
![Page 19: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/19.jpg)
Summary
L
v
L
vf
L
v
l
vf
L
v
L
vf
L
v
L
vf
L
vf
2
5
25
2
24
2
3
23
22
2
5
4
3
2
1
fn=nf1
fn= nth harmonic
n = 1, 2 ,3, …..
f1 =1st harmonic (fundamental frequency)
![Page 20: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/20.jpg)
Conditions for interference
L2
L1
P
δ = path difference = L2 – L1
Constructive Interference
δ = 0, λ, 2λ, 3λ …….
δ = nλ n = 0, 1, 2, 3, …
Destructive Interference
δ = λ/2, 3λ/2, 5λ/2 …….
δ = (n+ ½)λ
n = 0, 1, 2, 3, ….…
![Page 21: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/21.jpg)
Sound Waves
• The speed of sound in air at room temperature is 340m/s.
• The speed of sound increases with increasing temperature.
• The speed of sound in water is 1500m/s.
• The speed of sound in aluminum is 5100m/s.
![Page 22: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/22.jpg)
Physics Human
Perception
frequency
Intensity/Amplitude loudness
Pitch
![Page 23: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/23.jpg)
Pressure fluctuations in air due to a vibrating tuning fork.
Applet
![Page 24: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/24.jpg)
Frequency range of the human ear.
![Page 25: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/25.jpg)
Ultra Sound
![Page 26: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/26.jpg)
Human Ear
![Page 27: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/27.jpg)
Sound intensity and the decibel scale
![Page 28: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/28.jpg)
![Page 29: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/29.jpg)
Beats
• Beats occur when two sound waves have slightly different frequencies interfere with one another.
• The number of beats per second is called the beat frequency.
• The beat frequency is determined by subtracting the two frequencies.
![Page 30: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/30.jpg)
![Page 31: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/31.jpg)
Standing Sound Waves in a Tube
• The wave travels at the speed of sound (340m/s)
• Open ends must have an antinode• Closed ends must have a node.• A pressure wave is set up in the tube.• A tube open at both ends acts just like the
string.• A tube closed at one end only has odd
harmonics.
![Page 32: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/32.jpg)
Open Tube
3
23
LL21 L2
L
vf
L
vf
L
vf
2
3
2
3
2
1
Just like the string
![Page 33: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/33.jpg)
Closed Tube
5
45
LL41
3
43
L
L
vf
L
vf
L
vf
4
54
34
5
3
1
Odd Harmonics
![Page 34: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/34.jpg)
Resonance occurs when the driving frequency matches the natural frequency, resulting in large amplitude vibrations. Here are some examples of resonance
• Pushing someone on a swing.
• The Tacoma Narrows bridge.
• Breaking a wine glass with a sound wave
• Earthquakes totally destroying some buildings and not damaging others.
![Page 35: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/35.jpg)
The Doppler Effect is a change in frequency (pitch) due to the relative motion of the sound source and observer.
• As the sound and listener approach each other the frequency is higher.
• As the sound and listener move away from each other the frequency is lower.
• The Doppler effect also occurs with light producing the red and green shift of distant stars.
• Doppler radar is used to track weather systems
![Page 36: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/36.jpg)
![Page 37: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/37.jpg)
![Page 38: Waves A disturbance in a medium that transfers energy and momentum](https://reader034.vdocuments.us/reader034/viewer/2022051819/5514db77550346b0338b55c4/html5/thumbnails/38.jpg)