Notes: Name: __________________________

Stamps: Period: _________

NNOTESOTES WWAVESAVES - S - SOUNDOUNDDirections: Fill in the blanks and boxes in the note panel. After notes are done, part of your homework is to fill in the sides with study questions and write a summary that demonstrates you understand what is important in the notes.

Wave Equations Questions Main Notes

Wave: The transfer of ____________ without the transfer of ____________.

Wave Diagram – # of wavelengths in the wave below_____

The Wave Equationsfrequency ( f )= how many ____________________ pass per second = How often, or frequent, something occurs

units: hertz (Hz) =

period ( T )= time it takes for 1 __________________ to pass by

units:

speed ( v ) = How __________ something moves

units:

Example 1:The wave above takes 10 seconds to pass by.

a.) What is its period?b.) What is its frequency?

Summary:

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Types of WavesQuestions / main ideas Main Notes

• Mechanical waves require ___________ (a medium) in order to travel

Examples:

• Electromagnetic waves ____________ require a medium. They can travel through empty space.

Mechanical Wave TypesTransverse Wave: medium vibrates _______________________ the direction the energy moves.

Longitudinal Wave: medium vibrates _______________________ the direction the energy moves.

Classify the following mechanical waves as transverse or longitudinal:

A wave at a ball game Guitar string Flag waving in the wind Sound wave

Shaking a rope Water wave Slinky

Transverse Longitudinal

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Electromagnetic Waves

• All EM waves travel at ______________m/s

• Radio Waves: ________________in the EM spectrum

• Visible light is a tiny section of the EM spectrum

• Visible light is between __________________ and _______________

Example:The diagrams below represent two periodic waves traveling in a uniform medium.

A.) What type of wave is shown above?

B.) What is the

wavelength of wave A?

C.) What is the wavelength of wave B?

Summary:

AB

2m

3

InterferenceQuestions Main Notes

superposition: when two or more waves _________________

• Waves do not affect each other’s _______________

This is why you can hear lines in a song.

• When superimposed, overall amplitude is the _________ of individual wave amplitudes

This explains why it gets louder when many people talk at once.

Draw each wave pulse before, during and after they meet.

BEFORE

DURING Waves above the rest position are positive Waves below the rest position are _________ Add them up

AFTER Waves pass through each other unaffected

Summary:

Sound – volume and pitchQuestions / Main ideas Main Notes

• Sound is a ________________ wave

• Speed depends on both the _______________ and temperature

• Fastest in _________________ (6000 m/s in steel)

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• Slower in _________________ (1500 m/s in water)

• Slowest in gases

Speed of sound in air

• v = __________m/s at 0° C

at average temp: 20° C, v =

If no temperature is given, assume the temperature is ___________

Example:If you hear lightning strike 3.0 seconds after seeing it, how far away did it strike?

Characterizing SoundSound waves are characterized by:

Pitch – “high” or “low” sounds

• Depends on _________________

• Young healthy human ear has a range of 20 Hz to 20,000 Hz• Human voice: 120 Hz to 20,000 Hz• Baby cry: 2000 Hz to 3000 Hz

Frequency and pitch are important in music

• In music, an ______________is a doubling in f

Volume (loudness)

• Depends on the ______________ of a sound wave

• new unit _______________ (db)

• The decibel is based on human hearing

• 0 decibels is the threshold of ___________• Threshold is the quietist sound you can hear• 140 is the sound of a jet on a runway

• decibel scale is __________________

Continuous dB

Permissible exposure

85 8 hours

88 4 hours

91 2 hours

94 1 hour

97 30 min

100 15 min

103 7.5 min

106 3.75 min (<4 min)

109 1.875 min (<2 min)

112 0.9375 min (~1 min)

115 0.46875 min (~30 sec)

_________________

_________________

_________________

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Sound A

Sound B

Sound C

• So, 60 db 70 db means 10 louder• 60 db 80 db means 100 louder• 0 db to 140 db is 100,000,000,000,000x louder

Analyzing Sound Waves

1. For which sound(s) would youhear the lowest volume?

2. For which sound(s) would youhear the lowest pitch?

3. If you hear Sound B and Sound C what will be the same? What will be different?

Summary:

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Doppler EffectQuestions Main Notes

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Stationary Source

Moving Source – where would you stand to hear a higher pitch?

Doppler Effect occurs if either ____________ or ____________ is moving.

in front is ______________ than

the in back

in front is ______________ than

the in back

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•ƒ’ = frequency the ___________ hears

•ƒ = actual frequency of ___________

•v = speed of sound (___________ )

•vo = speed of ___________

•vs = speed of ___________

Picking SignsEx: On a day when the speed of sound is 350 m/s, a police car with a 2,000 Hz siren and a speed of 35 m/s is chasing a car moving at 50 m/s. What frequency does the driver of the car hear?

What is the source?

What is the observer?

Given:

Time to pick signs!

NumeratorIf observer travels away from source, pitch goes _______

•for pitch to go __________, vo must be __________

If observer travels towards source, pitch goes ________

•for pitch to go __________, vo must be __________

DenominatorIf source travels away from observer, pitch goes _______

•for pitch to go __________, vs must be __________

If source travels toward observer, pitch goes _______

•for pitch to go __________, vs must be __________

Our observer is moving ______________ source ( )

Our source is moving ______________ observer ( )

observer hears a ______________ pitch

ƒ =

v =

vo =

vs =

9

Summary:

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When the Source is faster than the SoundQuestions Main Notes

Mach Speed (pronounced: mock)• A plane traveling at the speed of sound is traveling at ___________

• NASA space shuttles travel at ________ – that’s 25 times the speed of sound!

Sonic Booms Objects moving faster than sound create shock

waves from the compressed air.

An observer hears this as a ___________ or BOOM!

The boom is caused by multiple overlapping wave crests which ____________ interfere

Which plane is moving faster?

The four figures below represent sound waves emitted by moving source.

1. Which picture(s) represent(s) a source moving at less than the speed of sound?

2. Which picture(s) represent(s) a source moving at the speed of sound?

3. Which picture(s) represent(s) a source moving faster than the speed of sound?

Summary:

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Standing Waves & ResonanceQuestions Main Notes

Standing Waves

• Occur when two waves _____________ each other

• The second wave is usually a _________________

• The _____ and _____ of each wave must be equal

• The parts that are motionless are called _________________

o Points _____________ are nodes

• The parts where A reaches a maximum are called _________________

o Points ____________ are antinodes

• The simplest standing wave (Wave A) is called the fundamental

• Wave A is in the ____________ of vibration

• Wave B is in the 2nd mode

• Wave C is in the 3rd mode

Questions1. Which standing wave has the greatest wavelength

2. The shortest?

3. How many wavelengths are shown in each standing wave?

Ex: If the string above is 3 m long and in first mode of vibration (A), what is the wavelength of the standing wave?

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Resonance

• Most physical systems have a __________________, which are easy to excite

• Vibrations keep moving if driven at their natural frequency

• This produces ____________waves

Examples of Resonance:1.

2.

3.

4.

Changes in Mediums

• Waves ________ & change _______ when they change mediums

• Reflected wave creates standing waves (resonance)

• Transmitted wave is what you hear

Wave Speed Wave speed depends on the _________ and _________ of the medium

Waves in Strings travel _________ than waves in Airo (Strings are more dense than air)

Waves in Stings travel _________ than waves in Woodo (Strings are less dense than air)

Wave Reflection• Reflected waves create __________ waves (resonance)

o Waves traveling from String to Wood bridge of a violin

Less à More dense: Reflection is closed and ___________

o Waves traveling from constricted air (tuba or flute) to free air

More à Less dense: Reflection is open and ____________

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Wave Reflection & Transmission

Summary:

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BeatsQuestions Main Notes

•  A beat is an oscillation in ____________

• Beats are caused by constructive and destructive __________

• Let’s look at two tuning forks at slightly different ________________

• The alternation between loud and soft is caused by _____________

• The beat frequency (______________) is equal to the _____________ in frequencies of the two tones

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Example:If two people stood near each other and whistled, one

with a frequency of 204 Hz and the other with a frequency of 214 Hz, how many beats would people hear in 10 seconds?

o Within 1 second you would hear ___ beats

o In 2 seconds you would hear ___beats

o So, within 10 seconds you would hear ____ beats

Summary

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Polarized LightQuestions Main Notes

• Light is a ____________ wave

• The wave below shows how this would appear

• If we looked at this wave head on it would appear as a line going up and down

• Naturally occurring light has waves on _______________

• This type of light is called ______________ light

• Polarized light is made of waves vibrating in _________ plane

• Let’s imagine unpolarized light in just ________ planes of vibration

• Vertical wave drawn as an arrow

• Horizontal wave drawn as a dot

How do you get Polarized light?

There are 3 methods of polarization:

• Selective Absorption

• ______________________

• Double Refraction

Selective Absorption

• A film of molecules stretched out in same ___________

• These molecules absorb all the light in that _________

• Remaining 50% (perpendicular to molecules) passes through the film

• 2 filters lined up 90° to each other will block _______%

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Reflection

• The horizontal component of light tends to ___________ off transparent surfaces (glare)

• The vertical component of light tends to ____________

• Not a perfect polarization

• When the reflected ray and the refracted ray are 90° from each other…

• They are both totally polarized

Polarizing Sunglasses

• Polarized sunglasses only block light that is vibrating ____________ (the glare)

• Real polarizing sunglasses will not work if you turn your head

Double Refraction

• Vertical component and horizontal component refract ___________

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• This gives two separate polarized rays

• All light is blocked out with two ________________ filters

• One ___________ out the horizontal the other the vertical

• Stress lines shown if it is a double refractor

Summary:

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