2 Mechanical Waves Require a medium to travel. Transverse, Longitudinal, Surface
3 Wave Description Frequency Unit Equation How frequently a wave pulse occurs.UnitHertz (Hz)1 Hz = 1/seconds or s-1Equation
4 Wave Description Period Equation The time (in seconds) that it takes for one wave to pass.EquationT = Period (in seconds)
5 Wave DescriptionFrequency and Period are Inversely Related
6 Types of Waves Transverse Waves Matter moves perpendicular to the direction of wave movement.
7 Types of Waves Longitudinal Waves Matter moves parallel to the direction of wave movement.
8 In the standing wave shown, what is the amplitude? In the standing wave shown, what is its wavelength?In the standing wave shown, how many nodes are there?
9 Key PrinciplesTransverse wave particles vibrate perpendicular to the wave direction and longitudinal wave particles vibrate parallel to the direction of the wave propagation.Sound waves are mechanical longitudinal waves. Light waves are electromagnetic transverse waves.The speed of a wave depends only on the properties of the medium.The energy of a wave is directly proportional to the square of the amplitude.Superposition Principle: When two or more waves exist simultaneously in the same medium, the resultant amplitude at any point is the algebraic sum of the amplitudes of each wave.
11 Wave Encounters When a wave meets an object 4 things could happen Reflection – wave bounces in new directionRefraction – wave bends as it passes thruDiffraction – wave bends as it passes aroundAbsorption – wave is absorbed and disappears
12 Superposition Principle Constructive vs destructiveMoving waves allow for this to change as the wave moves
13 Key Principles - SoundThe speed of a wave depends only on the properties of the medium.The intensity of sound is inversely proportional to the distance.The harmonics produced in open pipes are similar to those produced in strings.The fundamental occurs when the length of the pipe (or string) equals 1/2 λ.The fundamental on a closed pipe occurs when the length of the pipe equals 1/4 λ. Only the odd harmonics are possible for a closed pipe.Whenever two waves exist simultaneously in the same medium and they are nearly at the same frequency, beats are set up.Doppler effect is the apparent change in frequency of a source of sound when there is relative motion of the source and the listener.
15 vsolids > vliquids > vgases Wave SpeedSpeed of sound is determined only by the medium it travels through.The closer the molecules are, the faster it travels.Sound travels fastest through solidvsolids > vliquids > vgasesSlower than sound is subsonicFaster than sound is supersonicMaterialSound SpeedAir330Helium965Water1530Wood2000Gold3240Steel5940
16 Sound Wave Properties Pitch is determined by frequency Most sound waves have multiple frequencies – timbreEnergy determines loudness of the soundIntensity decreases as the wave moves away from the sourceLoudness measured in decibels
17 Intensity Scales Examples Hearing threshhold 0 dBWhisper 20 dB 102XOrdinary talk 60 dB XJackhammer 90 dB XIPOD Maxed dB XFront Row Concert 110 dB XPain Threshold 130 dB 1013X
18 Doppler Effect Effect of moving objects and sound waves Sound waves get closer together as the source approachesSound waves spread out as the source goes away
19 Resonance Every wave has a natural frequency Constructive interference increases energy causing resonanceIncreased amplitude = increased energy
20 HarmonicsAlmost all sounds are a mix of various frequencies – harmonics. Different mixes can produce the same overall frequency but a slightly different sound….