Exam 1 (Thursday, September 22, 2011)Physics in Entertainment and the ArtsCovers:- Act I40 multiple choice questions (2 points per question)08.30.11Lecture Notes:- Three kinds of waveso Transverse (most important) Medium moves perpendicular to the wave direction Can only happen in a media where the molecules are connected to one another Amplitude is how far molecules are displaced from their normal position Examples:- Water, lighto Longitudinal (fairly important) Medium moves back-and-forth, parallel to the direction of the wave Can happen with any type of medium Amplitude: (same) how far molecules are displaced from their normal position Examples:- Sound, earthquake waves o Torsional (not very important at all) Medium twists around the direction of travel Only solid mediums Examples:- Bone fracture, drive shaft, bridge from film/worksheet(λ) Wavelength: the length of a whole wave(A) Amplitude: half the total displacement(T) Period: time for one complete cycle(f) Frequency: number of cycles per second(V) Wave speed: f x λf = 1/T or T = 1/f09.01.11Lecture NotesTwo ways to picture a wave:1. Snapshot a. All points at one timeb. As a camera would see itc. Or, your eyes, if you blink once2. Frog-on-a-posta. One point at all timesb. Moment-by-moment report of positionc. Stream of data that we can graphThe resulting wave would be the same in every way except for the phase. Phase: staring position in the cyclePeriod (time) + wavelength (distance): both measure the extent or “reach” of a wave(one wavelength per period)If we have a snapshot of a wave, the horizontal span (x-axis) is distance. (wavelength - λ )If we have a frog-on-a-post wave, the horizontal span (x-axis) is time. (period – T)Most important idea of the course!Standing wave: family of waves that fit in a bounded medium.Nodes: points not moving a lotAntinodes: points moving a lotCan tell frequency by amount of nodes.09.06.11Lecture NotesStanding wave: a wave that fits in a bounded medium -> echoes must come backNode: where nothing seems to be happening in a standing wave- Waves and echoes are always interfering destructively (cancel each other out)Antinode: where the loops are the biggest, alternating constructive and destructive interferenceWhy does it sound:- Different set of standing waves- Force a node at a different spot09.08.11Lecture Notes*handout on VistaSpeed is set by the medium the wave is in.V = f x λ3 letters (NAN) = ½ λ5 letters (NANAN) = λFundamental/First Harmonic foor f1¿¿ simplest, longest, most basic wave L = ½ λλ = 2L Second harmonicf2 = 2 foL = λThird harmonicf3 = 3 foL = 3/2 λNth harmonicfN = N foL = N/2 λN antinodesN + 1 nodesHarmonics are your friends!Harmonic number tells you:1. Number of antinodes2. Multiple of fundamental frequencies3. How many waves fitPowerpoint: Interference in sound – beats, when two sounds make silenceBeats:- The “wah-wah-wah” sound when two very similar frequencies sound together- The result of alternating constructive and destructive interference - The beat frequency is simply the difference between the two frequencies- The slower the “wahs” the more nearly in tuneDifference in f = beats/secTime between beats: beat period09.13.11Film: Julius Sumner Miller09.15.11Lecture NotesA lot about the Doppler Effect: see also the powerpoint - The apparent shift in frequency due to the relative motion of a source of waves or an observer (car driving past you; change in sound)o Could come from the motion of the sourceo Could come from the motion of the observer- Applies to sound, water, light and light’s “relatives”Ultrasound: a frequency too high to hearWorks with light – too hard to notice, frequency determines colorRadio waves – speed gunsWeather forecasting – measures wind speeds too09.20.11Review notesf = how frequently something happensV = f x λIf a wave is not as tall (smaller A) – softer pitchIf a there are more waves, a shorter period (λ) – higher pitch λ - the same, set by stringLongitudinal waves will travel more quickly than transverse waves, in any one medium.Distance: x-axis: snapshot graph – span λ (cannot know period)Time: x-axis: frog-on-a-post graph – span period (T)When adding waves together, the new λ of combo is equal to the longest λ out of the original waves.Most independent – VMost dependent – λSupersonic Jet: A: hear nothing B: hear boom C: hear low pitchThe sharper the cone, the faster the