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Unformatted text preview: H133: 1094 Session 1 lSOLUEDNSE Write your name and answers on this sheet and hand it in or the end. There are a variety of activities today; watch the time and try to get through them all. Work with
others at your table on these activities. Argue about the answers but work efficiently! 1. 01: Group Problems [15 min.] a. Introduce yourself to the other students at your table. “\EVMM 30 X3: 36595:).
b. Problem Q1118: Draw pictures to illustrate our answer. 1" n ﬂ ‘ M _ was \rX‘? w
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sees em tests ass 15mm; b L 2 L5 5x Mumwwy cm\ ms . . . W .3. Ensure.
c.. Problem QIS.5 (Note: The pitchpf a sound you hear lS detennmed by Hi frequeqa): I mm;
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“43 \ LL 3 M NC"; ‘Solnlw‘ Uri“. ammo. LiﬁLli 19% C?“ “M o P :36 mp em I Q t d. Hint: you might ﬁnd the animated images of colliding and reﬂecting pulses on the H133 webpage of
use! . The diagram below represents a snapshot of two springs at an instant after a pulse has reached the
bound between them.
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#35 \ 1 meﬁ sis a. On the diagram, clearly label which spring has the larger wave speed. Explain how you
could tell from the diagram. Elli were uncle UM lee» goiter—n Mo: £05m \Obuodmj‘f?%&e b. Is the reﬂection at the boundary between the springs more like reﬂection from a fixed end or
a free end? Explain how you can tell from the diagram. Like. 0 \ﬁcouagcih twigs oil mm 50M ’Sﬁ‘l illwa c. On the diagram, label which ptﬂse is the reﬂected pulse and which is the transmitted pulse.
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2. Fourier Transforms and Guitar Physics [15 min.] Start up the PhET applet "Fourier: Making Waves" (Start>Programs>PhET. choose "Sound 8:; Waves" from
the left menu, and click once on the Fourier icon). ' You can set the amplitudes of sine wave to add together by dragging the bars with the mouse or changing the numbers under A], A2, etc. The "Sum" graph shows the net result. Try some different
amplitudes to get a feel how the waves combine. ' Now reset A1 = l and ﬁgure out the coefﬁcients needed to build up a square wave according to
equation (Q1.14). What values did you set for A2 and A3? 9‘3""— "NO as ’— fk 3?:
The Fourier transform theorem says that these coefficients are unique! You only have low freque i 3
available; what parts of the square wave are not reproduced? it “"‘k WNW {53W 9 5
m ou’i‘ «renovating. ' Try the "Wave Game" (middle tab). Start at Level 1, where you have one amplitude to adjust. Then try Level 4. (And then move on!) The sound from a plucked guitar string results from a superposition of the fundamental vibration and various
harmonics. The relative weighting of these vibrations determines the tonal "color" of the note, and is ﬁxed by how you pluck the string. Supporr your answers to the following questions with an observation from a demo
in class, or Q} discussion or homework problem, or the PhET simulation. a. "The strin s on a guitar are all the same length. Why do they lay differ nt not 5? G
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"To \‘3 "Ea: Who. No v vows KN §Pimjslnetausg new? M99 91;— cvb @065qu «(REM a) diget‘. Ben glam] b. If you want a sound with more highfrequency harmonics, should you pluck the string so that it initially
has a sharp or rounded bend? Should you luck it in the middle or toward on 3321? sh To, make 3 New M mm W“ more “oak \WWDMLD )‘SO “‘13 Wm’l 0“? Barb w\\\ kaQ mm "M? Q‘ﬂkﬁﬁ tosmmiﬁ» (R W QUL‘p'mmfm \0. maxim Wmomtj (Gwen or bewmilt‘ig growl" m ‘ "'33 \~\\\ he exciﬁah so Q‘N‘k Thwth 3% swat c. Invent a way to start a string vi rati g at only the fundamental frequency. gray “in (growwhisk m We)? “in (5% 0 Hits ch 65% o simwsve. " . of NM o3? Roommate a Q vent; 3K) EXCAQ ﬁfths) %sooaice 9mm} cam he. "Lousmh \Oﬁﬂdw‘ a? meet. oerellED . 3. Q2: Wave Interferenece and iffraction [15 min.] Start up the "Wave Interference" PhET applet (also under "Sound & Waves") and switch to the "Light" tab.
The simulation shows a light wave. Click on "Show Screen” and "Intensity Graph". You have control of the
wavelength and amplitude of the wave. and of one or two slits. a. With No Barrier, what does the intensity graph show? Hogan(N iiﬁ%ﬁgi>r\j) b. Now select "One Slit". Compare the simulation to Figures Q2.l and Figure (22.10. What is the width of
the intensity plot? Predict what will happen if you decrease the wavplenggh. What dictually halﬁens if
you Chang to purple light? bikgmtfﬁm «mm m at C513": 5753‘ r 1 , 50 (“113m
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\acqamaamum \Wa “tour \9 Willa? (1‘90:le Gig, _ c. Now switch to "Two Slits" and answer twominute p oblem Q2T.2 usir§your bserva%9ns of the \ XL
applet (i.e._3_play with the controls!). 911 h hem 3‘“: 50444 Wheean a at“ 50”)?" 566T'Siéj fly a?) X’i‘ln LEE} heath {9 ed LIV h’l‘
b3 iii an) mists tang) one is stratum Smbig d. At Prof. Fumstahl's house, his small stereo speakers ("tweeters") are Carefully positioned but the big W ' subwoofer is hidden behind the couch. How can he get away with a *5. egabs grid
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 Spring '11
 Furnstahl
 Quantum Physics

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