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June 07, 2016
Do Now
June 07, 2016
Review Quizzes
Make sure the record for quiz scores is pasted in your notebook.
I will be keeping a record on skedula, but you should also be recording your scores.
Individual scores DO NOT COUNT towards your grade.
Your overall mastery score will be counted as an exam grade.
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Example
Susie Student takes all 10 review quizzes. However, on kinematics and circular motion, she scores less than 80%. Susie has two options.
1. Do nothing. She has mastered 8 of the 10 review topics and will receive an exam grade of 80%.
2. Come to tutoring and then do a re-take. If she masters both the second time, she will receive an exam grade of 100%.
June 07, 2016
WHAT IS A WAVE?
A ripple forms when raindrops hit the pond.What is the source?What is the medium?
(move the green dot here to reveal answer)
A ripple forms when raindrops hit the pond.What is the source?What is the medium?
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Which way is the wave moving?
How are the individual people moving?
What is the wave carrying down the line of people?
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Transverse Wave
A wave travels along its medium, but the individual particles just move up and down.
Phet.
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What's the relationship between frequency and wavelength?
Copyright (c) The University of Colorado, under the GNU General Public License (GPL)
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PARTS OF A TRANSVERSE WAVE
amplitude crest trough wavelength
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Key Points
Waves don't carry particles forward, waves only transmit
energy.
The Amplitude of a wave is directly related to the amount of energy it transmits.
In a transverse wave, the particles move perpendicular to the direction of the wave.
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Wave Motion
Wave characteristics:• Amplitude, A• Wavelength, • Frequency f and period T• Wave velocity
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Wave Motion
Wave velocity is the velocity at which wave crests (or any other part of the wave) moves.
A wave crest travels a distance of one wavelength, , in one period, T.
Wave velocity is:
June 07, 2016
1 What is the wave speed if the period of a wave is 4 seconds and the wavelength is 1.8 m?
Ans
wer
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2 A fisherman noticed that a float makes 30 oscillations in 15 seconds. The distance between to consecutive crests is 2 m. What is the wave speed?
Ans
wer
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3 What is the wavelength of a wave traveling with a speed of 6 m/s and a period of 3s?
Ans
wer
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Wave Motion
The velocity of a wave depends on the medium through which it is traveling.
The velocity of a wave on a stretch string is related to the tension force in the string and the mass per unit length of the string.
Where FT is the tension in the string and is the mass per unit length (m/L).
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4 What happens to the speed of a wave on a string if the tension of the string is increased by a factor of nine?
A It is decreased by a factor of 3.
B It is decreased by a factor of 9.
C It is increased by a factor of 3.
D It is increased by a factor of 9.
Ans
wer
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5 What happens to the speed of a wave on a string if the mass per unit length of the string is increased by a factor of nine?
A It is decreased by a factor of 3.
B It is decreased by a factor of 9.
C It is increased by a factor of 3.
D It is increased by a factor of 9.
Ans
wer
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Types of Waves: Transverse and Longitudinal
The motion of particles in a wave can either be perpendicular to the wave direction (transverse) or parallel to it (longitudinal).
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Types of Waves: Transverse and LongitudinalSound waves are longitudinal waves:
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Reflection and Transmission of WavesA wave reaching the end of its medium, but where the medium is still free to move, will be reflected (b), and its reflection will be upright.
A wave hitting an obstacle will be reflected (a), and its reflection will be inverted.
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Reflection and Transmission of Waves
A wave encountering a denser medium will be partly reflected and partly transmitted; if the wave speed is less in the denser medium, the wavelength will be shorter.
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Reflection and Transmission of Waves
A wave encountering a lighter medium will be partly reflected and partly transmitted; if the wave speed is greater in the denser medium, the wavelength will be longer.
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Interference; Principle of SuperpositionThe superposition principle says that when two waves pass through the same point, the displacement is the arithmetic sum of the individual displacements.
In the figure below, (a) exhibits destructive interference and (b) exhibits constructive interference.
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Reflection and Transmission of WavesTwo- or three-dimensional waves can be represented by wave fronts, which are curves of surfaces where all the waves have the same phase.
Lines perpendicular to the wave fronts are called rays; they point in the direction of propagation of the wave.
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Interference; Principle of SuperpositionThese figures show the sum of two waves. In (a) they add constructively; in (b) they add destructively; and in (c) they add partially destructively.
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6 What is the result at an oscillating point if two waves reach this point one half of a wavelength apart?
A Constructive interference
B Destructive interference
C Partially destructive interference
Ans
wer
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7 What is the result at an oscillating point if two waves reach this point two full wavelengths apart?
A Constructive interference
B Destructive interference
C Partially destructive interference
Ans
wer
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8 What is the result at an oscillating point if two waves reach this point one quarter of a wavelength apart?
A Constructive interference
B Destructive interference
C Partially destructive interference
Ans
wer
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Do Now
If the frequency of the wave pictured below is 4Hz, find the period and speed of the wave.
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Quick Wave Review
Waves transfer ______________
A wave where the particles move at a right angle to the direction of the wave is called a _________________
A wave where the particles move parallel to the direction of the wave is called a _________________
____________ is the number of complete waves per unit time
__________ is the time it takes for one complete wave to pass
Frequency and period are ___________ proportional to each other
Two points on a wave that are moving in the exact same way at the same time are said to be _____________
Describe the behavior of a wave when it encounters a fixed boundary.
Describe the behavior of a wave when it encounters a free boundary.
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Name two points that are in-phase
Name two points out of phase
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InterferenceConstructive = two waves combine, larger amplitudeDestructive = amplitudes of two waves combine, producing a smaller amplitude
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DiffractionWhen a wave passes a barrier or moves through a hole in a barrier, it bends and spreads out.
Diffraction = the bending of waves around the edge of a barrier
http://www.echalk.co.uk/Science/Physics/rippleTank/ripple.htm
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Diffraction
Diffraction occurs when a wave moves around a barrier or through an opening in a barrier, it bends and spreads out .
Diffraction waves
Another example of diffraction would be sound as it bends around a corner and you can hear it.
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Doppler Effect
Return to Tableof Contents
June 07, 2016
Doppler EffectThe Doppler effect occurs when a source of sound is moving with respect to an observer.
Click here for a video on
the doppler effect
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Doppler Effect
As can be seen in the previous image, a source moving toward an observer has a higher frequency and shorter wavelength; the opposite is true when a source is moving away from an observer.
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9 If a sound source is moving toward the listener. The listener will experience an __________ in the pitch of sound that he or she hears.
A increase
B decrease
Ans
wer
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10 If a sound source is moving away from the listener. The listener will experience an __________ in the pitch of sound that he or she hears.
A increase
B decrease
Ans
wer
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Doppler EffectIf the observer is moving with respect to the source, things are a bit different. The wavelength remains the same, but the wave speed is different for the observer.
However, the effect is much the same. The observed frequency goes up as you go towards a sound source, and down if you go way from one.
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Shock Waves and the Sonic Boom
If a source is moving faster than the wave speed in a medium, waves cannot keep up and a shock wave is formed.
Click here for a video on
the sound barrier
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Standing Waves; Resonance
Standing waves occur when both ends of a string are fixed. In that case, only waves which are motionless at the ends of the string can persist.
There are nodes, where the amplitude is always zero, and antinodes, where the amplitude varies from zero to the maximum value.
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Standing Waves; Resonance
The frequencies of the standing waves on a particular string are called resonant frequencies.
They are also referred to as the fundamental and harmonics.
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Standing Waves; ResonanceThe wavelengths and frequencies of standing waves are:
(11-19a)
(11-19b)
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10m
13 If the speed of the wave is 8m/s, what is the frequency of this wave?
Ans
wer
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SummaryVibrating objects are sources of waves, which may be either a pulse or continuous.
Wavelength: distance between successive crests.
Frequency: number of crests that pass a given point per unit time.
Amplitude: maximum height of crest.
Wave velocity:
For a wave on a string:
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SummaryTransverse wave: oscillations perpendicular to direction of wave motion.
Longitudinal wave: oscillations parallel to direction of wave motion.
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SummaryWhen two waves pass through the same region of space, they interfere. Interference may be either constructive or destructive.
Standing waves can be produced on a string with both ends fixed. The waves that persist are at the resonant frequencies.
Nodes occur where there is no motion; antinodes where the amplitude is maximum.
Waves refract when entering a medium of different wave speed, and diffract around obstacles.
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