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CU-Boulder PHYS 1240 - Questions

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1Ct 4.1.xWhich kind of reflection is far andaway the most common forlight, in ordinary life?A) SpecularB) Diffuse4.1.2I play a bass note facing an indoorclimbing wall, the sound is reflected offthe surface, what will happen? (the notehas a wavelength of about 5 meters)a) The sound will largely reflect diffuselybecause the surface is roughb) The sound will largely reflect specularlybecause the surface is smoothc) The sound will all be absorbed because thesurface is roughd) The sound will diffract because the bumpsand holes are smalle) ??CT 4.1.4If the bumps and irregularities on the wallare about 30 cm wide (or smaller), whichfrequencies of sound are most likely toreflect diffusely? (I.e. what’s the “cutoff”?)A) Frequencies above 10 HzB) Frequencies below 10 HzC) Frequencies above 1000 HzD) Frequencies below 1000 HzE) ???4.2.1How can it be that a sound produced by A reaches B ifthe wall between them strongly absorbs sound?(Which is the best reason?)(Assume other walls are smooth)a)Because the sound reflects onceb)Because the sound reflects many timesc)Because of diffraction through the openingd)Some other reason is most importante)It wouldn’t reach BAB24.2.2If you hear the following two waves inyour left and right ear where would youlikely perceive the sound coming from?From…a) … above youb) … below youc) … your rightd) … your lefte) ??Time(seconds)Over Pressure (N/m2) Left EarOver Pressure (N/m2) Time(seconds)Right Ear4.5.1Looking at the following two waves:Here they are graphed together:Which of the waveforms shown below represents the sum of theabove two?a) Pinkb) Greenc) Blued) Rede) None of theseTime(seconds)Over Pressure (N/m2)Time(seconds)Time(seconds)Time(seconds)Over Pressure (N/m2)Over Pressure (N/m2)Over Pressure (N/m2)4.5.2Same question as before, but just a tad harder…And graphed together…Which is a representation of the sum of thetwo waveforms?a) Pinkb) Greenc) Blued) Rede) ??Over Pressure (N/m2)Over Pressure (N/m2)Time(seconds) Time(seconds)Over Pressure (N/m2)Time(seconds)Over Pressure (N/m2)Time(seconds)4.5.2Which pairs of tones would have a slowvery distinct beat?a) 10 Hz and 20 Hzb) 100 Hz and 120 Hzc) 100 Hz and 102 Hzd) None of thesee) Not enough information34.5.3Suppose there are two tones. The first toneis 440 Hz and the second is 442 Hz. What would happen to the beats, if the second tone was lowered to 438 Hz?a) The beats would be more frequent.b) The beats would be less frequent.c) The beats would be a little softer.d) The beats would be a little louder.e) Nothing.CT4.5.4xSuppose the two speakers in theroom are playing the same steadyfrequency, but one is “reverse wired”(so they’re exactly out of phase) I’mstanding on the “midline”. What do Ihear?A) Steady, loud pitchB) Steady pitch, same as either oneof the speakers aloneC) SilenceD) BeatsE) Something else/???CT 4.5.2xTwo waves traveling in the samedirectionImagine two traveling sin waves (samefrequency, in phase, or “in synch”)traveling together (same direction,starting in the same place)What happens when they “superpose”?A) A traveling wave, same as either oneindividuallyB) A traveling wave, twice the amplitudeof either oneC) A traveling wave that gets bigger andsmaller, bigger and smaller, inamplitude (beats)D) A standing waveE) ?? (something else)CT 4.5.2xbTwo waves traveling in oppositedirectionsImagine two sin waves (same frequency)traveling towards each other (oppositedirections, passing through each other),What happens when they “superpose”?A) A traveling wave, same as either oneindividuallyB) A traveling wave, twice the amplitude ofeither oneC) A traveling wave that gets bigger andsmaller, bigger and smaller, in amplitude(beats)D) A standing waveE) ?? (something else)4CT 4.2.3You can hear a sound in your left earthat came from your right.There are many physical reasons why thisoccurs, but which below is best?a) Because your head is a relatively roughsurfaceb) Because of interferencec) Because the sound just keeps travelingthrough your head to your left ear drumd) Most sound wavelengths are larger than yourhead so they diffracte) Most sound wavelengths are smaller thanyour head so they diffractCT 4.2.4Which sounds are more likely tohead out only in the forwarddirection from a large speaker?A) The low pitchesB) The high pitchesC) All pitchesD) None…(Why might we choose to usesmaller speakers for treble?)Ct 4.2.5Would light also diffract if youpass it through a slit?A) SureB) Only if the slit is muchSMALLER than the wavelengthof lightC) Only if the slit is muchLARGER than the wavelength oflightD) ???Decent diffraction if λ > hole sizes4.4.3Given the following picture of asound source and its sound wavesin still air, what do you conclude?a) The source is movingb) The source is stationaryc) There is some obstruction to theright of the sourced) The sound being produced is ofvarying pitch and wavelengthe)???s54.4.4The picture below shows a travelingobject that is emitting a sound. There is aperson at point A and a person at pointB. Which direction is the sound traveling?a) Rightb) Leftc) All directionsd) Need more informationWho hears the higher pitch?a) Ab) Bc) They hear the same pitchd) Need more informationA B4.4.2A child is swinging on a swingtowards a person blowing a whistle.At which position will the pitchsound the highest to the child?d. The pitch is the same at all thepoints.Whistlera.b.c.endstart4.3.1Adding a shell around a performer at anoutdoor show…a) Improves the music no matter where theperformer is positioned or where the audiencesitsb) Subtly alters the pitch of the sound, makingit more pleasing to normal hearingc) Diffracts the music better, allowing biggeraudience to heard) Is mostly for aesthetic purposes/protectionfrom raine) Could increase the loudness for theaudience, depending on where the performer ispositioned within the shell.Where should the performer stand toget the maximum benefits out of thiscircular shell?d)Somewhere elsee)There is no


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CU-Boulder PHYS 1240 - Questions

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