Yr 10 Physics Outline of key concepts 2012:

□ Types of wave: transmission of energy by transverse and longitudinal type waves with reference to compressions, rarefactions.

□ Graphing waves: interpret/draw amplitude versus time wave diagrams as well as amplitude versus displacement diagrams, and to be able to recognise amplitude, period and/or wavelength.

□ Sound: knowledge as a longitudinal wave, speed of sound in different mediums.□ Understanding of how pitch relates to frequency/period and loudness relates to amplitude.□ Knowledge of range of human hearing and limitations as we grow older.□ How tones can sound musical and the mathematical relationship between the frequency of these tones, in particular

whole number multiples of the fundamental frequency.□ Understanding of the term resonance.□ Interpretation of standing waves and resonance questions.□ Understanding of how most complex tones are a combination of multiples of the fundamental harmonic.□ Being able to comprehend/interpret spectrum analysis plots in terms of fundamental and consequent harmonics for

complex tones. E.g answering questions about harmonics graphs.□ Understand how instruments can be used to create music.□ Electromagnetic spectrum: knowledge of how energy radiation versus low energy, and qualitative relationship

between frequency and wavelength, as on p116. All em travels at speed of light in space.□ Calculations involving v = fλ.□ Calculations involving f = 1/T.□ Polarisation of light.□ Magnetic Fields: Knowledge of the field patterns of bar magnets and solenoids and that of the earth.□ How magnetism can be created electrically, how to construct an electromagnet.□ The existence and nature of the force that magnetism places on moving electrons□ Synchrotron: Know at least three different uses for it.□ Be able to describe the fundamentals of how a synchrotron beam is produced using the terms: electron gun, linac,

booster ring, storage ring, beamline, experimental station.□ How magnetism is used to guide beam lines. □ Understand the meaning of diffraction and interference.□ Nature of synchrotron light: polarisation, coherency, brightness and why this is an advantage. □ Range of available radiations in the synchrotron.

Contents:Breaking the silence vid.. p2Speed of sound questions p3Middle C assignment p4-6Resonance in spring prac p6Physics of music vid p7-9Using the oscilloscope, calculating frequency from waveform, determining harmonics. p10-12Related harmonics questions p13-14Wave equations – simple p15Wave questions involving sound using both f=1/T and v =fp16-18A lightly story – vid p19-20Mapping magnetic fields p21wave experiment to determine c(speed of light) p22-23General notes and wave questions p24-35Basic revision wave quests: p36-40

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Video: VC 534 BRE C3137 Breaking the Silence: Yr 10 science: Name: The following questions may be answered while watching the video or upon its conclusion.

Q1. What causes all sounds?...................................................................................................................................Q2. Give five examples of things vibrating that cause a sound...............................................................................................................................................................................................................................................................Q3. What is necessary to cause something to vibrate?.............................................................................................Q4. Name some examples of sources of energy that can cause sound......................................................................................................................................................................................................................................................Q5. What determines whether a sound is loud or soft?............................................................................................

...............................................................................................................................................................................Q6. What does the term frequency mean?..............................................................................................................

...............................................................................................................................................................................Q7. In what units is frequency measured?...............................................................................................................Q8. What is the lowest frequency that humans can hear?.........................................................................................Q9. What is the highest frequency that humans can hear?........................................................................................Q10. What determines whether a sound is high or low?...........................................................................................Q11. What is the highness or lowness of a sound called?.........................................................................................Q12. How are pitch and volume different? Describe................................................................................................

...............................................................................................................................................................................Q13. On a stringed instrument describe three ways in which the pitch of a string can be altered.

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Q14. How can the pitch of a note be changed on a wind instrument?.......................................................................

...............................................................................................................................................................................Q15. How does sound travel through air?................................................................................................................

Q16. Describe how humans can hear/receive sound waves......................................................................................

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...............................................................................................................................................................................Q17. Can sound travel through other materials other than air? Does it travel differently in other materials? Describe an example of this...................................................................................................................................................

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Q18. Describe how you can hear an echo of your own voice...................................................................................

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Year 10 Physics The Speed of SoundTo complete this sheet you will need to refer to page 114 of your text book (Science Quest 4)Also d=vtWhere d is distance (metres)

V is velocity (metres per second)t is time (seconds)

1. Calculate the distance travelled by a sound wave travelling in air for 5.4 seconds

2. Calculate the distance travelled by a sound wave travelling in sea water for 1.6 seconds

3. A sound wave travels a distance of 680m in 2.62 seconds. What substance is it probably travelling through?

4. How long would it take an American fighter jet (travelling at Mach 1) to cover 2300 km (in seconds)?

5. The Brazilians claim that they have an even faster jet that covers 6012 km in 10 minutes. Does it travel faster than the American jet?

6. Joe and Jack are watching a storm (with fork lightning). Jack tells Joe that he can accurately measure the distance from the lightning bolt to where they are standing. To do this he downloads an “app” to his i-phone (one that can accurately measure time). Jack sees a lightning bolt and then using his “app” is able to measure that it takes 2.03 seconds to hear the thunder. Explain, in terms of waves, why jack saw the lightning before he heard it.

7. Jack then does a calculation to work out the distance from the lightning bolt. His answer was 710 meters. Is he correct? Support your answer using a relevant calculation.

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YEAR 10 PHYSICS ASSIGNMENT 1CONSTRUCTING A MUSCIAL INSTRUMENT

Task: Design, construct and evaluate a simple musical instrument using low cost materials.Your instrument is to be designed so it will play Middle C (256Hz(old) or 262Hz(new-since 1940’s).Bring your instrument to class and demonstrate what it can doSubmit a written report with test results from the sound analyzer found in Data studio

Details: (Check the assessment criteria at the end of this handout)1. Introduction to your written report: This should include sufficient background information about sound

and musical instruments. (What is sound? Different ways in which different instruments make sound) 2. Materials used and the construction process. Include all the experimenting that you did, including any

aborted constructions. Time spent and when you spent the time. This is best presented in diary form. You need to be able to state the total time you spent on this project. INCLUDE A DIAGRAM THAT SHOWS YOUR INSTRUMENT

3. Describe how you tuned your instrument, you need something that plays middle C. If you don’t have an instrument at home use WAVEGENSHARE(freeware on internet), to generate a sound of exactly 262Hz.

4.5. At school obtain from the oscilloscope software osc251(also freeware on internet)

(i) A graph of several periods of the wave form(ii) The harmonic spectrum, these can be both sketched by hand from what you see on the screen, with any numerical values quoted.

MAKE SURE THESE GRAPHS ARE CLEARLY TITLED, AND MAKE REFERENCE TO THEM IN THE DISCUSSION OF THE PERFORMANCE OF YOUR INSTRUMENT.(there is little point putting them in if you don’t refer to them)

6. Evaluation:(a)Does your instrument make musical sounds?(b)Can you improve it by changing a particular part or by changing the size of a part?

(c) Discuss how you could change the frequency or the loudness of the sound that it makes.

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(d) Describe the tone of your instrument. Does it sound pure and simple like a tuning fork or does it seem fuller and more complex like a clarinet?

(e) State how close you got to middle C, list the number of harmonics and their frequencies .

(f)Does the waveform suggest a complex sound and presence of a large number of harmonics.?)

WHERE DO I START?Think of some different musical instruments and how they work, see if you can examine one closely. You can then design and make your own instrument using a variety of materials. Here are some suggested starting points.

Unfortunately there is very little to construct by filling a bottle to a suitable depth, bottles will not be accepted.

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Yr 10 Physics AssignmentAssessment sheet.

Name: ……………………………………………………………………………………………………..

Assessment Criteria:

Instrument:Creativity 0 1 2 3 4 5Use of materials 0 1 2 3 4 5Presentation(appearance) 0 1 2 3 4 5Durable construction 0 1 2 3 4 5Audibility 0 1 2 3 4 5Ability to play C 0 1 2 3 4 5

Not shown - poor -satisfactory – good - very good - excellentReport:Introduction 0 1 2 3 4 5Construction process 0 1 2 3 4 5Diagram of Instrument 0 1 2 3 4 5Accurate log 0 1 2 3 4 5Waveform/Spectrum 0 2 4 6 8 10Evaluation 0 3 6 9 12 15Summary 0 1 2 3 4 5(Logical/neat presentation 0 2 4 6 8 10

Total: /90marksComments:

Please attach this sheet to your report, and sign below that you have included all the points from the assessment rubric above:

Signature………………………………………………………

Date:…………………………………………………………

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Comment on the accuracy of the results you obtained, make mention of how and where measuring errors could have occurred.

Write the “simple rule” that gives the relationship between the fundamental frequency and the frequency of each successive harmonic in :

Words:

An Equation:

( where fn is the frequency of the nth harmonic and ff is the fundamental frequency)Play some music that contains only harmonicsGo and look at the Tacoma bridge!Research, how long was it resonating like above?

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Name................................................Physics of music - Video

1. Complete the following sentence:

Sound waves are made up of a series of C_____________________ and R____________________2. What does a microphone turn pressure variations into?

....................................................................................................................................................3. What is music made up of?

....................................................................................................................................................4. What is noise?

....................................................................................................................................................5. What is another term for pitch? What are the units?

....................................................................................................................................................6. What happens to the loudness of a sound as amplitude is decreased?

....................................................................................................................................................Part 2

7. What makes instrument sounds different from each other even when they are playing the same note?

....................................................................................................................................................

....................................................................................................................................................8. Describe how you could produce a complex wave?

....................................................................................................................................................

....................................................................................................................................................9. In a stringed instrument, what is:

(a) The primary vibrator? .................................................................................

(b) The resonant vibrator?.................................................................................

10. How does increasing the mass of a string change the nature of a note?

....................................................................................................................................................11. How does increasing the tension in a string change the nature of a note?

....................................................................................................................................................12. Describe how a standing wave can be produced?

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................13. Describe the process by which a wine glass or a violin produces a note.

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....................................................................................................................................................

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....................................................................................................................................................14. What causes beats?

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....................................................................................................................................................16. When can notes be described as being most ‘pleasing to the ear’?........................................................................................................................................................................................................................................................................................................

15. What are the three components of all musical instruments?

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................16. What does resonance do to a sound?

....................................................................................................................................................

....................................................................................................................................................17. What is a node?

....................................................................................................................................................18. What is an antinode?

....................................................................................................................................................

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PIANO 256 Hz, middle C as capture by an oscilloscopePiano256Hz

The overall resultant waveform is quite complicated yet does repeat itself. This gives this piano its characteristic sound

The spectrum analysis supports the complicated waveform showing 8 significant harmonics:256,2256=512, 3256=768, 1024,1280,1536,1792,2048.The 1st, 2nd, 3rd and 5th harmonics being dominant.

The relative intensities of the harmonics is what determines what the tone sounds like.Ie whether it is a trumpet or a violin or a good violin.

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This slider can be used to control the horizontal scale. The sweep number says how many Hz for the horizontal section. For each grid divide by 10.Each grid represents 259Hz.

This slider is used to control the amplitude of the wave. Adjust so it is of a size that fills most of the screen

This is to toggle between two different horizontal scales

Play(make OSC active) Pause(freeze display) Toggle between wave and spectrum

The controls above are the only ones you need to adjust.To print the display you must copy it into a word document. To do this PrtSc(top right of your keyboard and paste into Word. You can trim the ‘fat’ of the image by first pasting it into ‘Paint’ by selecting only the oscilloscope and therefore not end up pasting the rest of your desktop into your document, also invert the colour to save toner when you print!.

We need to be able to state the % that each harmonic contributes to the overall tone.For the Piano tone there are eight significant frequencies that make up the overall tone.To work out % of each follow the following procedure:

The method below represents a more accurate way of obtaining the exact frequency of the waveform.Evaluating the frequency from the waveform display rather than the Spectrum Analyser view

You will be required to use this way in your project.

A typical waveform may look like the above. The time that has been pictured is represented by SWEEP.

USE THE CONTROLS T and Y1 to create one wavelength on the screen.

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Method Measure the height of each peak on the graph- count squares.Add up the total heights.Work out each height as a % of the totalIe for the first harmonic:

Harmonic Height % of total1 4.5 192 7.3 313 1.6 74 0.5 25 7 306 0.5 27 0.8 38 1.2 5

Total 23.4 100

You must evaluate these and include them in the report for

The sweep value is 3.86ms (Time for one complete cycle of the waveform)This means 3.86/1000=0.00386 s

The frequency of the note is given by:

-----------------------------------------------------------------------------------------------------------------------------------------

Sometimes it is impossible to adjust T so there is exactly one wave on the screen:

The frequency of the note can also be evaluated by the following formula(which is an adaptation of the previous one)

ie There is ~6 waves taking a time of 23.51ms

WHISKEY BOTTLE 256 Hz

Notice the simplicity of the above wave form. The sound obtained by blowing across a bottle is a very pure type of sound, giving an almost perfect wave.

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The spectrum analysis shows only one significant peak at 256 HZ, showing that the tone consists only of the 1st harmonic of 256 Hz

GUITAR STRING 256Hz

The spectrum analysis suggests a complicate waveform:There are 9 identifiable harmonics above at 256,512………….2034HZThe 1st, 2nd being very dominant and the 4th and 9th harmonics being significant.Although the spectrum of the guitar string is just as complicated as the piano string they are significantly different.

Compare the overall wave form with that of the whiskey bottle and the piano.

Some harmonics questions:

1. Sketch the 2nd and 3rd harmonics for a vibrating string of 10cm in length.

2. If the frequency of the fundamental tone of the string is 250Hz, find the frequency of the 3rd harmonic.

3. The frequency of the 4th harmonic of a string is observed to be 800Hz, find the frequency of the 5th Harmonic.

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4. A vibrating rubber band resonsates at a frequency of 400Hz, the next frequency it resonates at is 600Hz. What is the lowest frequency that it will resononate at? Explain your answer.

5. A harmonic spectrum is taken from a single note played on the piano(262.5Hz middle C). The first line on the plot corresponds to the frequency 262.5Hz.

6.

(a) What is the name given to the first line(from the left)

(b) What is the general name used to describe the other lines?

(c) Is there any mathematical relationship between the frequency of the lines? If so state what it is.

(d) What do the presence of these additional lines do to the overall sound?

(e) How would the plot of the piano be different to a person who whistles middle C

7. Nigel is a very fussy concert pianist. He insists that he will only play pianos that have a particular overall tone. His requirement is that there should only be three even harmonics in the tone and that they should be dominant and of equal intensity. He is not fussed by the number of odd harmonics, but insists they should be no more than half the intensity of the even harmonics.

Given that you have to find such a piano, show on the spectrum below what you would be looking for when you sample the sound, the fundamental is already included.

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The Wave Equation

V = fλ

Where v is velocity (in metres per second)f is frequency (in hertz)

λ is wavelength (in metres)

and

T = 1/f or f = 1/T

Where T is the period (in seconds)f is frequency (in hertz)

1. Andrew observes that 8 waves (ripples) arrive at the beach in 4 secondsa. What is the frequency of the wavesb. What is the period of the waves

2. A wave generator in a ripple tank produces 15 wave pulses in 3.4 secondsa. What is the frequency of the wavesb. What is the period of the waves

3. The same wave generator as mentioned in Q2 is shown to produce waves with a wave length of 2.3 cm. What is the velocity of the wave (in m/s)?

4. A sound wave is found to have frequency of 700Hz and a wavelength of 0.5 metres. a. What is the velocity of the sound wave?b. What is the period of the sound wave?

5. A sound wave travelling in wood is known to have speed of 4000 m/s. If the frequency of the wave is 812 Hz, find the wavelength.

6. A sound wave is found to have period of 0.25 seconds. Calculate it’s speed if it has a wavelength of 65 metres. What medium is this wave likely to be travelling through (refer page 114 of text)

7. An electromagnetic wave travels at the speed of light (3 x 108 m/s). If it has a wavelength of 65 cm, find its’ frequency and its’ period. Give your answers in Scientific Form and correct to two significant figures.

8. An infrared remote control produces waves with a period of 10-16 s. What is the frequency of the wave? Calculate the wavelength of the wave if it travels at the speed of light. Give your answers in Scientific Form and correct to two significant figures.

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A Lightly Story DVD 535, LIG D686, Yr 10 Physics1. ................ was a clue to the nature of light

2. Which Egyptian goddess swallowed the sun?.................

3. What was the Pythagorean theory of light?..........................

4. Where did the idea that light was rays come from?...........................

5. Another name given to spectacles was........................................, and was supposedly coined by............................

6. When were glasses first thought to be worn?........................................

7. Where did Galileo get the idea to make a decent telescope?......................................................................

8. Why was Copernicus’ theory not accepted at the time?....................................................................................

9. Kepler predicted that light was ..................bent by lenses

10. What behaviour of light cast doubt on the earlier theory that light was tiny particles?.............................................................................................................................................................

11. The death of Galileo and the birth of Isaac Newton coincided in what year?......................

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12. Describe the experiment done by Newton that led to the conclusion there is no such thing as ‘white’ light?

13. Which waves were longer, red or green?.....................................................14. What did question did Huygens contemplate in order to think of some other model for light other

than particles?........................................................................................................................................................

15. Why did Galileo’s speed of light experiments fail?

............................................................................................................................................................

...................

16. How was the first real accurate determination of the speed of light done?

............................................................................................................................................................

...................

17. Draw a diagram of Faraday’s experiment:

18. What was observed in the experiment?................................................................................................................

19. What did Faraday theorise makes the observation possible, a magnetic..................

20. James Maxwell worked on this idea and came up with a speed for the magnetic wave, what was it?........................................................

21. This led to the idea that light was an ........................... .......................... wave.

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Yr. 10 Physics: Mapping Magnetic field lines.

Aim: To be familiar with the use of a compass of detecting directions and locations of magnetic fields.Background: North(red) end of compass points in direction of magnetic field(B).

Method:

Place compass at A - move compass around in general area. Mark line where needle points for 5 different points within area A. How far can compass be moved away from A before needle reverts to influence of earth’s magnetic field?Repeat for Area B.Move compass in arcs E to I and from J to P label direction of field at points along the arcsFind direction of field at X.Do the observations you have made exist in three dimensions?, explain how you tested in the 3rd dimension.

Conclusion:

Using Cheese and a microwave to find the speed of light.21

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KL M

P

A B

X

Try this: cheese slices Want to stay healthy? Don't eat cholesterol laden cheese – use it to measure the speed of light!Warning: Melted cheese can burn. Take extra care.

You will need Cheese slices

a metric ruler

a microwave oven with no carousel or removable carousel

pen

paper

calculator

What to do 1. Remove carousel

2. Spread cheese slices over bottom of microwave, perhaps using a plate so the movement of the carousel drive doesn’t affect the cheese.

3. Heat the cheese on high power until it starts to melt in two or three spots - this usually takes about 40 seconds. You should stop before the cheese is nuked

4. Remove the cheese from the microwave and measure the distance between neighbouring globs of melted cheese.

Now for the calculations: 1. Measure the distance between melted spots.

D =

2. Multiply this by two to calculate the wavelength.

3. Show with the aid of a diagram why we need to multiply this distance by 2.

4. Establish the frequency of your microwave, its usually written on the back of the unit somewhere. Typical values are 2.45GHz, Giga = multiply by a billion or 109. Hence 2.45GHz = 2.45 x 109 Hz, this is the value that needs to be used in the equation v = f

f =

5. Calculate the speed of the microwaves according to v = fV =

6. How does it compare to c(speed of light at 3 x 108 m/s)?

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What's happening? Microwaves are a form of electromagnetic radiation, like x-rays and radio waves. All electromagnetic radiation travels at the speed of light. This means the microwaves in your microwave oven are travelling at the speed of light. Electromagnetic radiation travels in waves. The frequency is how often these waves go up and down – it is the measure of the peak of one wave to the peak of the next wave. The hot spots in your chocolate are half the wavelength, as a wave will pass through the chocolate bar twice as it goes through a cycle.Once you have the wavelength and the frequency it is easy to calculate the speed as the wavelength multiplied by the frequency gives the speed.

Applications Microwaves are great for heating up food, but aren't actually hot. This was accidentally discovered by Dr. Percy Spencer around 1946.Percy had been working on a magnetron, a type of radar, which gives off short bursts of microwaves to detect incoming planes. He'd left a chocolate in his pants and it melted because of a microwave burst – not just because it was a hot day.Percy realised the importance of his discovery and blasted some popcorn kernels with microwaves from the magnetron. This was fluffy microwave popcorn's world debut!Percy's microwave cooking had limited success – next he tried cooking raw eggs, but the pressure rose too quickly and the eggs burst (don't try that at home).Microwaves pass through glass, paper, pastry, fats and most china. Water, however, absorbs microwaves very well. The microwaves ‘shake' the water molecules, making them vibrate about 2.45 billion times each second. As the molecules vibrate, they rub against each other and the friction produces heat for cooking.Microwaves can be used for more than just cooking. Here are some other technologies that use microwaves:

radar

radio astronomy

wireless computer networking, including Bluetooth

some pay TV

some mobile phone networks, like GSM.

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Notes

 Compressions are regions of high air pressure while the rarefactions are regions of low air pressure.

The wavelength of a wave is merely the distance which a disturbance travels along the medium in one complete wave cycle.

Since a sound wave consists of a repeating pattern of high pressure and low pressure regions moving through a medium, it is sometimes referred to as a pressure wave.

 The above diagram can be somewhat misleading if you are not careful. The representation of sound by a sine wave is merely an attempt to illustrate the pressure-time fluctuations. Do not conclude that sound is a transverse wave which has crests and troughs.

  Pitch and Frequency The vibrating object is the source of the disturbance which moves through the medium. Regardless of what vibrating object is creating the sound wave, the particles of the medium through which the sound moves is vibrating in a back and forth motion at a given frequency. A commonly used unit for frequency is the Hertz (abbreviated Hz), where

1 Hertz = 1 vibration/second

Since a sound wave is a pressure wave, a detector could be used to detect oscillations in pressure from ahigh pressure to a low pressure and back to a high pressure.

The diagram below shows two pressure-time plots, one corresponding to a high frequency and the other to a low frequency.

The ears of a human (and other animals) are sensitive detectors capable of detecting the fluctuations in air pressure which impinge upon the eardrum.

The sensation of a frequencies is commonly referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave.

two sounds whose frequencies make a 2:1 ratio are said to be separated by an octave and result in a particularly pleasing sensation when heard. That is, two sound waves sound good when played together if one sound has twice the frequency of the other.

Interval Frequency Ratio ExamplesOctave 2:1 512 Hz and 256 Hz

 

The ability of humans to perceive pitch is associated with the frequency of the sound wave which impinges upon the ear 

Check Your Understanding

1. A sound wave is different than a light wave in that a sound wave is

a. produced by an oscillating object and a light wave is not. b. not capable of traveling through a vacuum.

c. not capable of diffracting and a light wave is.

d. capable of existing with a variety of frequencies and a light wave has a single frequency.

   1. A sound wave is a pressure wave; regions of high (compressions) and low pressure (rarefactions) are established as the result of the vibrations of the sound source. These compressions and rarefactions result because sounda. is more dense than air and thus has more inertia, causing the bunching up of sound. b. waves have a speed which is dependent only upon the properties of the medium.

c. is like all waves; it is able to bend into the regions of space behind obstacles.

d. is able to reflect off fixed ends and interfere with incident waves

e. vibrates longitudinally; the longitudinal movement of air produces pressure fluctuations.

1. Two notes which have a frequency ratio of 2:1 are said to be separated by an octave. A frequency which is separated by an octave from middle C (256 Hz) is

a. 128 Hz b. 254 Hz c. 258 Hz

d. 345 Hz e. none of these

  The Speed of Sound

A sound wave is a pressure disturbance which travels through a medium by means of particle-to-particle interaction.

Since the speed of a wave is defined as the distance which a point on a wave (such as a compression or a rarefaction) travels per unit of time, it is often expressed in units of meters/second (abbreviated m/s). In equation form, this is

speed = distance/timeFactors Affecting Wave Speed

The speed of any wave depends upon the properties of the medium through which the wave is traveling. Typically there are two essential types of properties which affect wave speed - inertial properties and elastic properties.

Elastic properties

In general, solids have the strongest interactions between particles, followed by liquids and then gases. For this reason, longitudinal sound waves travel faster in solids than they do in liquids than they do in gases.

vsolids > vliquids > vgases

The density of a medium is an example of an inertial property. The greater the inertia (i.e., mass density) of individual particles of the medium, the less responsive they will be to the interactions between neighboring particles and the slower that the wave will be. A sound wave will travel faster in a less dense material than a more dense material. Thus, a sound wave will travel nearly three times faster in Helium as it will in air. This is mostly due to the lower mass of Helium particles as compared to air particles.

The speed of a sound wave in air depends upon the properties of the air, namely the temperature and the pressure. At high pressure the particles interact more quickly and the speed is greater. At high temperature the particles have more energy and the speed is greater.

Using Wave Speed to Determine Distances

At normal atmospheric pressure and a temperature, a sound wave will travel at approximately 343 m/s; Light travels through air at a speed of approximately 300 000 000 m/s; For this reason, humans can observe a detectable time delay between the thunder and the lightning during a storm. The arrival of the light wave from the location of the lightning strike occurs in so little time that it is essentially negligible. Yet the arrival of the sound wave from the location of the lightning strike occurs much later.

For instance if the thunder is heard 3 seconds after the lightning is seen, then sound (whose speed is approximated as 345 m/s) has traveled a distance of

distance = v x t = 345 m/s x 3 s = 1035 m

Another phenomenon related to the perception of time delays between two events is an echo.

For instance if an echo is heard 1.40 seconds after making the holler, then the distance to the canyon wall can be found as follows:

distance = v x t = 345 m/s x 0.70 s = 242 m

The canyon wall is 242 meters away. You might have noticed that the time of 0.70 seconds is used in the equation.

While an echo is of relatively minimal importance to humans, echolocation is an essential trick of the trade for bats

The Wave Equation Revisited

The mathematical relationship between speed, frequency and wavelength is given by the following equation.

Speed = Wavelength x FrequencyUsing the symbols v, , and f, the equation can be rewritten as

v = f x

An alteration in wavelength does not affect (i.e., change) wave speed. Rather, an alteration in wavelength affects the frequency in an inverse manner. A doubling of the

wavelength results in a halving of the frequency; yet the wave speed is not changed. The speed of a sound wave depends on the properties of the medium through which it moves and the only way to change the speed is to change the properties of the medium.

Check Your Understanding

1. An automatic focus camera is able to focus on objects by use of an ultrasonic sound wave. The camera sends out sound waves which reflect off distant objects and return to the camera. A sensor detects the time it takes for the waves to return and then determines the distance an object is from the camera. If a sound wave (speed = 340 m/s) returns to the camera 0.150 seconds after leaving the camera, how far away is the object?

2. On a hot summer day, a pesky little mosquito produced its warning sound near your ear. The sound is produced by the beating of its wings at a rate of about 600 wing beats per second.

a. What is the frequency in Hertz of the sound wave? b. Assuming the sound wave moves with a velocity of 350 m/s, what is the wavelength of the wave?

3. Doubling the frequency of a wave source doubles the speed of the waves.

a. True b. False

4. Playing middle C on the piano keyboard produces a sound with a frequency of 256 Hz. Assuming the speed of sound in air is 345 m/s, determine the wavelength of the sound corresponding to the note of middle C.

5. Most people can detect frequencies as high as 20 000 Hz. Assuming the speed of sound in air is 345 m/s, determine the wavelength of the sound corresponding to this upper range of audible hearing. 

6. An elephant produces a 10 Hz sound wave. Assuming the speed of sound in air is 345 m/s, determine the wavelength of this infrasonic sound wave. 

8. Miles Tugo is camping in Glacier National Park. In the midst of a glacier canyon, he makes a loud holler. He hears an echo 1.22 seconds later. The air temperature is 20 degrees C. How far away are the canyon walls

 9. Two sound waves are traveling through a container of unknown gas. Wave A has a wavelength of 1.2 m. Wave B has a wavelength of 3.6 m. The velocity of wave B must be __________ the velocity of wave A.

a. one-ninth b. one-third

c. the same as d. three times larger than

  10. Two sound waves are traveling through a container of unknown gas. Wave A has a wavelength of 1.2 m. Wave B has a

wavelength of 3.6 m. The frequency of wave B must be __________ the frequency of wave A.

a. one-ninth b. one-third

c. the same as d. three times larger than

 

Resonance and Standing WavesNatural FrequencyThe frequency or frequencies at which an object tends to vibrate disturbed is known as the natural frequency of the object. The quality or timbre of the sound produced by a vibrating object is dependent upon the natural frequencies of the sound waves produced by the objects. Some objects tend to vibrate at a single frequency and they are often said to produce a pure tone. Other objects vibrate and produce more complex waves with a set of frequencies which have a whole number mathematical relationship between them; these are said to produce a rich sound.Still other objects will vibrate at a set of multiple frequencies which have no simple mathematical relationship between them. These objects are not musical at all and the sounds which they create could be described as noise.

The actual frequency at which an object will vibrate at is determined by a variety of factors. Each of these factors will either affect the wavelength or the speed of the object. Since

 As we know from our understanding of the frequency-wavelength relation, a shorter air column means a shorter wavelength and a higher frequency.

Consider a guitar string vibrating at its natural frequency or harmonic frequency. Because the ends of the string are attached and fixed they string are unable to move. Subsequently, these ends become nodes - points of no displacement. In between these two nodes at the end of the string, there must be at least one antinode. The most fundamental harmonic for a guitar string is the harmonic associated with a standing wave having only one antinode positioned between the two nodes on the end of the string. This would be the harmonic with the longest wavelength and the lowest frequency. The lowest frequency produced by any particular instrument is known as the fundamental frequency. The fundamental frequency is also called the first harmonic of the instrument.

The second harmonic of a guitar string is produced by adding one more node between the ends of the guitar string. This additional node gives the second harmonic a total of three nodes and two antinodes. The third harmonic of a guitar string is produced by adding two nodes between the ends of the guitar string. And of course, if two nodes are added to the pattern, then two antinodes must be added as well in order to maintain an alternating pattern of nodes and antinodes.

After a discussion of the first three harmonics, a pattern can be recognized. Each harmonic results in an additional node and antinode, and an additional half of a wave within the string. If the number of waves This information is summarized in the table below.

Harm.#

# ofWaves

in String

# ofNodes

# ofAnti-nodes

1 1/2 2 12 1 or 2/2 3 23 3/2 4 3

      

Check Your Understanding1. The sound produced by blowing over the top of a partially filled soda pop bottle is the result of the air column inside of the bottle vibrating at its natural frequency. The actual frequency of vibration is inversely proportional to the wavelength of the sound; and thus, the frequency of vibration is inversely proportional to the length of air inside the bottle. Express your understanding of this resonance phenomenon by filling in the following table.  

  The Speed of a WaveThe speed is the distance traveled by a given point on the wave (such as a crest) in a given interval of time. In equation form,

If the crest of an ocean wave moves a distance of 20 meters in 10 seconds, then the speed of the ocean wave is 2 m/s. When a wave undergoes reflection, it remains within the medium and merely reverses its direction of travel. you often hear the echo of the holler. The sound wave travels through the medium (air in this case), reflects off the canyon wall and returns to its origin (you). Noah stands 170 meters away from a steep canyon wall. He shouts and hears the echo of his voice one second later. What is the speed of the wave? In this instance, the sound wave travels 340 meters in 1 second, so the speed of the wave is 340 m/s. Remember, when there is a reflection, the wave doubles its distance. In other words, the distance traveled by the sound wave in 1 second is equivalent to the 170 meters down to the canyon wall plus the 170 meters back from the canyon wall. Variables Affecting Wave Speed

What variables affect the speed at which a wave travels through a medium? Waves travel through tighter ropes at higher speeds. So while the frequency did not affect the speed of the wave, the tension in the medium (the rope) did. In fact, the speed of a wave is not dependent upon properties of the wave itself. Rather, the speed of the wave is dependent upon the properties of the medium such as the tension of the rope.

Check Your Understanding1. A teacher attaches a slinky to the wall and begins introducing pulses with different amplitudes. Which of the two pulses (A or B) below will travel from the hand to the wall in the least amount of time? Justify your answer.

 2. The teacher then begins introducing pulses with a different wavelength. Which of the two pulses (C or D) will travel from the hand to the wall in the least amount of time ? Justify your answer.

 3. The time required for the sound waves (v = 340 m/s) to travel from the tuning fork to point A is ____ .

a. 0.020 second b. 0.059 secondc. 0.59 second d. 2.9 second

  4. Two waves are traveling through the same container of nitrogen gas. Wave A has a wavelength of 1.5 m. Wave B has a wavelength of 4.5 m. The speed of wave B must be ________ the speed of wave A.a. one-ninth b. one-thirdc. the same as d. three times larger than5. An automatic focus camera is able to focus on objects by use of an ultrasonic sound wave. The camera sends out sound waves which reflect off distant objects and return to the camera. A sensor detects the time it takes for the waves to return and then determines the distance an object is from the camera. If a sound wave (speed = 340 m/s) returns to the camera 0.150 seconds after leaving the camera, then how far away is the object?6. TRUE or FALSE:Doubling the frequency of a wave source doubles the speed of the waves.7. While hiking through a canyon, Noah Formula lets out a scream. An echo (reflection of the scream off a nearby canyon wall) is heard 0.82 seconds after the scream. The speed of the sound wave in air is 342 m/s. Calculate the distance from Noah to the nearby canyon wall.8. Mac and Tosh are resting on top of the water near the end of the pool when Mac creates a surface wave. The wave travels the length of the pool and back in 25 seconds. The pool is 25 meters long. Determine the speed of the wave.

 9. The water waves below are traveling along the surface of the ocean at a speed of 2.5 m/s and splashing periodically against Wilbert's perch. Each adjacent crest is 5 meters apart. The crests splash Wilbert's feet upon reaching his perch. How much time passes between each successive drenching? Answer and explain using complete sentences.

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The Nature of a WaveWhat is a Wave?A wave can be described as a disturbance that travels through a medium . The particle might be moved upwards or downwards, forwards or backwards; but once moved, it is returned to its original equilibrium or rest position. A pulse is a single disturbance moving through a medium from one location to another location.

 A medium is a substance or material which carries the wave. Particle-to-Particle InteractionConsider the presence of a wave in a slinky. The first coil becomes disturbed and begins to push or pull on the second coil; this push or pull on the second coil will displace the second coil from its equilibrium positionSubsequently, the disturbance travels through the medium. The medium can be pictured as a series of particles connected by springs.. 

A Wave Transports Energy and Not Matterthe individual particles of the medium are only temporarily displaced from their rest position. Waves are said to be an energy transport phenomenon. As a disturbance moves through a medium from one particle to its adjacent particle, energy is being transported from one end of the medium to the other. In conclusion, a wave can be described as a disturbance which travels through a medium, transporting energy from one location (its source) to another location without transporting matter. Each individual particle of the medium is temporarily displaced and then returns to its original equilibrium positioned.  

Check Your Understanding1. TRUE or FALSE: In order for John to hear Jill, air molecules must move from the lips of Jill to the ears of John.2. Curly and Moe are conducting a wave experiment using a slinky. Curly introduces a disturbance into the slinky by giving it a quick back and forth jerk. Moe places his cheek (facial) at the opposite end of the slinky. Using the terminology of this unit, describe what Moe experiences as the pulse reaches the other end of the slinky. 3. Mac and Tosh are experimenting with pulses on a rope. They vibrate an end up and down to create the pulse and observe it moving from end to end. How does the position of a point on the rope, before the pulse comes, compare to the position after the pulse has passed? 4. Minute after minute, hour after hour, day after day, ocean waves continue to splash onto the shore. Explain why the beach is not completely submerged and why the middle of the ocean has not yet been depleted of its water supply. 5. A medium is able to transport a wave from one location to another because the particles of the medium are ____.a. frictionless b. isolated from one anotherc. able to interactd. very light 

Color and VisionThe Electromagnetic and Visible Spectra

The Electromagnetic and Visible SpectraAs discussed in Unit 10 of The Physics Classroom Tutorial, electromagnetic waves are waves which are capable of traveling through a vacuum. Unlike mechanical waves which require a medium in order to transport their energy, electromagnetic waves are capable of transporting energy through the vacuum of outer space. Electromagnetic waves are produced by a vibrating electric charge and as such, they consist of both an electric and a magnetic component. The precise nature of such electromagnetic waves are not discussed in The Physics Classroom Tutorial. Nonetheless, there are a variety of statements which can be made about such waves.Electromagnetic waves exist with an enormous range of frequencies. This continuous range of frequencies is known as the electromagnetic spectrum. The entire range of the spectrum is often broken into specific regions. The subdividing of the entire spectrum into smaller spectra is done mostly on the basis of how each region of electromagnetic waves interacts with matter. The diagram below depicts the electromagnetic spectrum and its various regions. The longer wavelength, lower frequency regions are located on the far left of the spectrum and the shorter wavelength, higher frequency regions are on the far right. Two very narrow regions within the spectrum are the visible light region and the X-ray region. You are undoubtedly familiar with some of the other regions of the electromagnetic spectrum.

  Visible Light SpectrumThe focus of Lesson 2 will be upon the visible light region - the very narrow band of wavelengths located to the right of the infrared region and to the left of the ultraviolet region. Though electromagnetic waves exist in a vast range of wavelengths, our eyes are sensitive to only a very narrow band. Since this narrow band of wavelengths is the means by which humans see, we refer to it as the visible light spectrum. Normally when we use the term "light," we are referring to a type of electromagnetic wave which stimulates the retina of our eyes. In this sense, we are referring to visible light, a small spectrum from the enormous range of frequencies of electromagnetic radiation. This visible light region consists of a spectrum of wavelengths which range from approximately 700 nanometers (abbreviated nm) to approximately 400 nm. Expressed in more familiar units, the range of wavelengths extends from 7 x 10-7 meter to 4 x 10-7 meter. This narrow band of visible light is affectionately known as ROYGBIV.Each individual wavelength within the spectrum of visible light wavelengths is representative of a particular color. That is, when light of that particular wavelength strikes the retina of our eye, we perceive that specific color sensation. Isaac Newton showed that light shining through a prism will be separated into its different

wavelengths and will thus show the various colors that visible light is comprised of. The separation of visible light into its different colors is known as dispersion. Each color is characteristic of a distinct wavelength; and different wavelengths of light waves will bend varying amounts upon passage through a prism. For these reasons, visible light is dispersed upon passage through a prism. Dispersion of visible light produces the colors red (R), orange (O), yellow (Y), green (G), blue (B), and violet (V). It is because of this that visible light is sometimes referred to as ROY G. BIV. (Incidentally, the indigo is not actually observed in the spectrum but is traditionally added to the list so that there is a vowel in Roy's last name.) The red wavelengths of light are the longer wavelengths and the violet wavelengths of light are the shorter wavelengths. Between red and violet, there is a continuous range or spectrum of wavelengths. The visible light spectrum is shown in the diagram below.

 When all the wavelengths of the visible light spectrum strike your eye at the same time, white is perceived. The sensation of white is not the result of a single color of light. Rather, the sensation of white is the result of a mixture of two or more colors of light. Thus, visible light - the mix of ROYGBIV - is sometimes referred to as white light. Technically speaking, white is not a color at all - at least not in the sense that there is a light wave with a wavelength which is characteristic of white. Rather, white is the combination of all the colors of the visible light spectrum. If all the wavelengths of the visible light spectrum give the appearance of white, then none of the wavelengths would lead to the appearance of black. Once more, black is not actually a color. Technically speaking, black is merely the absence of the wavelengths of the visible light spectrum. So when you are in a room with no lights and everything around you appears black, it means that there are no wavelengths of visible light striking your eye as you sight at the surroundings.  

Check Your Understanding1. A light wave is an electromagnetic wave which has both an electric and magnetic component associated with it. Electromagnetic waves are often distinguished from mechanical waves. The distinction is based on the fact that electromagnetic waves ______.a. can travel through materials and mechanical waves cannot b. come in a range of frequencies and mechanical waves exist with only certain frequenciesc. can travel through a region void of matter and mechanical waves cannotd. electromagnetic waves cannot transport energy and mechanical waves can transport energye. electromagnetic waves have an infinite speed and mechanical waves have a finite speed

   2. Consider the electromagnetic spectrum as you answer these three questions.a. Which region of the electromagnetic spectrum has the highest frequency? b. Which region of the electromagnetic spectrum has the longest wavelength?c. Which region of the electromagnetic spectrum will travel with the fastest speed?

 3. Consider the visible light spectrum as you answer these two questions.a. Which color of the visible light spectrum has the greatest frequency? b. Which color of the visible light spectrum has the greatest wavelength?

  Year 10 Science – Physics

Waves and SoundPutting it all Together

1) Compare transverse waves with compression waves. Include a diagram and an example of each in your answer.(Refer to your text book Science Quest 4 pages 112 – 117

2) Define each of the following words:a) medium (as it applies to waves)

b) frequency

c) pitch

d) wavelength

e) amplitude

3) Draw a transverse wave with a wavelength of 10 cm and amplitude of 2 cm.

4) Draw a labelled diagram to show the difference between a compression and a rarefaction(3 marks)

5) For a wave moving at a particular speed, what happens to the frequency as the wavelength decreases?

6) What units are used to measure frequency? Include the word and its abbreviation.

7) Give three differences between sound waves and electromagnetic waves.(Refer to p116 and 117 of your text book – Science Quest 4

8) List three examples of electromagnetic waves.

9) A flash of lightning is often followed several seconds later by the thunder it has caused. Explain, in terms of waves, why we see the lightning before we hear the thunder.

All waves have common properties:Property Symbol Definition UnitWavelength λ The distance between two identical points such as crest

to crest or trough to trough, compression to compression or rarefaction to rarefaction.

m

Amplitude A The height from the midpoint to its highest point or its lowest point

m

Frequency f The number of waves passing through a fixed point each second, measured in Hertz (Or the number of time the object making the sound vibrates each second)

Hz

Period T The time taken for one wavelength to pass a given point.

s

The Wave Equation

V=f λWhere v= speed (ms-1)

f= frequency (Hz)λ=wavelength (m)

Period and Frequency:

T = 1 f

Where T = period (s10. Year 10 Science students are conducting a slinky experiment. They are studying the effect of

different variables upon the speed of a wave. Their data table is shown below. Use this data to calculate the missing values in the table.

Medium Wavelength

Frequency

Speed

Zinc Slinky

(2.5cm diameter coils)

1.75m 2.0Hz

Zinc Slinky

(2.5cm diameter coils)

0.9m 3.9Hz

Copper Slinky

(2.5cm coils)

1.19m 2.5m/s

Copper Slinky

(2.5cm coils)

0.6m 4.2Hz

Zinc Slinky

(7.6cm diameter coils)

2.2Hz 2.1m/s

Zinc Slinky

(7.6cm diameter coils)

1.82m 2.18m/s

11. As the wavelength of a wave in a uniform medium increases, its speed will _____.

a. decrease b. increase c. remain the same

12. As the wavelength of a wave in a uniform medium increases, its frequency will _____.

a. decrease b. increase c. remain the same

13. A ruby-throated hummingbird beats its wings at a rate of about 70 wing beats per second.a. What is the frequency in Hertz of the sound wave? b. Calculate the period of the sound wave

c. Assuming the sound wave moves with a velocity of 350 m/s, what is the wavelength of the wave

Show all your workings in the space below.

14) A violin string has a length of 22 cm. It is vibrating in its fundamental mode at 920Hz. The speed of the sound through air is 340m/s.

(a) ................................................................What is the length of one wavelength on the violin string?

......................................................................................................................................................................(b) ..........................What is the velocity of a transverse vibration which travels along this violin string?

......................................................................................................................................................................

The speed of the sound through air is 340m/s.(c) .........................What is the frequency of the sound wave in air caused by the vibrating violin string.

......................................................................................................................................................................

15). A guitar string is 0.66m in length . When plucked in its centre it produces a fundamental frequency of 80 Hz. The guitarist presses the string against a fret, shortening the string to produce notes of different frequency. How long should the string be to produce a note of frequency

(a) ........................................................................................................................................... 160 Hz.........

(b) ........................................................................................................................................... 320Hz..........

1

(i)The two graphs above represent the behaviour of the same wave on a spring and appear identical, what is the difference between the two graphs?..............................................................................................................

(i) ......................................................................................................... What is the period of the wave. .

(ii) ................................................................................................What is the wavelength of the wave. .

(iii) .................................................................................................What is the amplitude of the wave. .

(iv) ........................................................................................................ What is the speed of the wave. .

(v) ................................................................................................... What is the frequency of the wave. .