Crave the Wave Mechanical Waves & Sound Waves—Class 2 - PowerPoint Presentation

1. Crave the Wave Mechanical Waves & Sound Waves—Class 22022-2023 SeasonRuss Burlesongeaux15@hotmail.com 1

2. AgendaBinder Check/Homework reviewMechanical Wave overviewTransverse WavesSurface WavesLongitudinal Waves (general)Sound Waves (Longitudinal)Homework2

3. Binder Check/Homework ReviewGet out your binder and find the following if found in under 10 seconds you winotherwise add and reorganizeFind in your binder (not quote from memory)Rule 2.bPhase velocity equation (three versions solving for frequency, velocity, and wavelength)Diagram showing how to find the wavelength of a waveAt least three separate electromagnetic spectrum diagrams3

4. Wave OverviewFrom Wikipedia, “a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities, sometimes as described by a wave equation”Usually Mechanical or Electromagnetic. Also can be Gravitational, Heat Diffusion, Plasma or Reaction-Diffusion Waves.Can be Periodic, which means that these quantities oscillate repeatedly about a resting value at some frequencyWhen moving in one direction only, it is a Traveling WaveWhen superimposed periodic waves travel in opposite directions, they can make a Standing Wavehttps://en.wikipedia.org/wiki/Wave4

5. GENERAL WAVE FEATURESThe diagram below gives you the most basic features of waves including amplitude, wavelength and frequency. It also shows the high point of a frequency curve (crest) and low points of a curve (trough).* Velocity = frequency times wavelength5

6. Velocity of a WaveTwo different types of wave velocitiesPhase Velocity is the rate at which the wave propagates in any medium. This is the velocity at which the phase of any one frequency component of the wave travels ν = λf (where ν is the phase velocity, λ is the wavelength, and f is the frequency) orν = λ/T (where ν is the phase velocity, λ is the wavelength, and T is the period)Group Velocity is the velocity with which the overall envelope shape of the wave's amplitudes—known as the modulation or envelope of the wave—propagates through spaceThe equations for group velocity are beyond the scope of this event, but generally it is the speed of the envelope that the wave travels withinhttps://en.wikipedia.org/wiki/Wave#Phase_velocity_and_group_velocityhttps://en.wikipedia.org/wiki/Phase_velocityhttps://en.wikipedia.org/wiki/Group_velocity6

7. Transverse String Waves Longitudinal Sound Waves Surface Water Waves Mechanical WavesOscillation of matter (water, sound, seismic, etc.)Requires an elastic and inertia based medium to propagate sound cannot travel in the vacuum of spaceThree subtypesTransverse Waves (medium vibrates perpendicular to direction of wave, think of a slinky or a string wave)Longitudinal Waves (medium vibrates parallel to direction of wave, think of a sound waves)Surface Waves (travels along the surface/interface of two media such as water waves or seismic waves)https://en.wikipedia.org/wiki/Mechanical_wavehttps://en.wikipedia.org/wiki/Transverse_wavehttps://en.wikipedia.org/wiki/Longitudinal_wavehttps://en.wikipedia.org/wiki/Surface_wavehttps://en.wikipedia.org/wiki/Sound7

8. Transverse WavesTransverse Waves (medium vibrates perpendicular to direction of wave, think of a guitar string, drum membrane, or a string wave)Electromagnetic Waves are also Transverse WavesTransverse Waves commonly occur in elastic solids due to shear stress (hence why Mechanical Transverse Waves cannot travel through liquids, but others can)Requires a mediumhttps://en.wikipedia.org/wiki/Transverse_wave Transverse String Waves Transverse Electromagnetic WavesTransverse Guitar String Waves 8

9. Surface WavesSurface Waves (a mechanical wave that propagates along the interface between differing media, think of ocean, Rayleigh, Love, some electromagnetic, or radio ground waves)Electromagnetic Waves can be surface waves in between two dielectrics or a dielectric and conductorSeismic waves such as Rayleigh or Love waves are also surface wavesradio transmission, a ground wave is a guided wave that propagates close to the surface of the EarthRequires two mediumshttps://en.wikipedia.org/wiki/Surface_wavehttps://en.wikipedia.org/wiki/Wind_waveSurface Ocean Waves Surface Seismic Rayleigh WavesSurface Seismic Love Waves 9

10. Seismic WavesSeismic Waves can be felt as Earthquakes.There are two typesBody Waves which travel through the EarthP, Primary, or Compression waves travel the fast (~6km/sec) with forward and backward similar to sound wavesS, Secondary or Shear Waves are slower (~3.5 km/sec) are side to sideSurface waves, which travel on the surface are slower and are the actual EarthquakesLove waves Shake the ground side to side like an S waveRayleigh waves are similar to rolling ocean wavesSeismographs measure small movements and by seeing the time difference in S and P waves, you can determine the distance to the epicenterUsing three measurements at different locations you can locate the specific epicenter10https://en.wikipedia.org/wiki/Seismic_wavehttp://www.columbia.edu/~vjd1/earthquakes.htmhttp://www.mgs.md.gov/seismic/education/no6.html

11. Seismic Waves MeasurementsFind the S and P times for each measuring stationFind the difference in time (or Δt)Find the distance from the S and P graph for that particular ΔtRepeat for two other measuring locations and where those circles of distance intersect is the epicenterApproximate speedsShear Waves ≈ 3.5 km/secCompression Waves ≈ 6 km/secDistance is approximately 8.4 • Δt (km)11http://www.columbia.edu/~vjd1/earthquakes.htm http://www.mgs.md.gov/seismic/education/no6.html

12. Longitudinal WavesLongitudinal Waves (medium vibrates parallel to direction of wave, think of sound waves)Also called Compression or Pressure WavesSound waves are most common and are vibrations in pressure in an elastic mediumSeismic Pressure (P-waves) can be created by earthquakes, explosions, etc.Requires a mediumhttps://en.wikipedia.org/wiki/Longitudinal_wavehttps://www.npr.org/2014/04/09/300563606/what-does-sound-look-likeLongitudinal Pressure WavesLongitudinal Spring/Slinky WavesLongitudinal Sound Waves12

13. Speed of SoundThe speed of sound depends on the medium the waves pass through, and is a fundamental property of the materialFormula for speed of sound was initially developed by Sir Isaac Newton and improved by Laplace, called the Newton-Laplace equation Speed of sound changes due to ambient conditions and materialsHigher temperature increases speedDifferent materials have different speeds with it normally traveling fastest in solids and slowest in gases (due to higher Bulk Modulus/stiffer material in solids) https://en.wikipedia.org/wiki/Soundhttps://en.wikipedia.org/wiki/Speed_of_soundShockwave/Sonic Boom from Breaking Sound BarrierSound Waves from a SpeakerMeasured Sound WavesK, c velocity of sound, density ϒ heat capacity ratio/Laplace coefficient, p pressure At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn)13

14. Speed of Sound as function of temperature in gasesGeneral formula for speed of sound in dry air General formula for ideal gases and air https://en.wikipedia.org/wiki/Soundhttps://en.wikipedia.org/wiki/Speed_of_soundc velocity of soundv temperature in ⁰C  At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn)c velocity of sound, ϒ adiabatic index/heat capacity ratio/Laplace coefficient, densityR Molar/Universal Gas Constant (8.314 J/K-mol), T absolute temperature (K), M molar mass of the gask Boltzmann constant (1.38*10-23 J/K), m mass of single molecule c velocity of soundT temperature in K  Please note that the speed of sound (in gas) is proportional to the square of pressure, absolute temperature (K), and the adiabatic indexInversely proportional to density, Molar Mass of the gas, and mass of a single moduleFor an ideal gas speed depends upon temperature only since pressure and density change in lockstep14

15. Speed of Sound as function of altitude in gasesTemperature is still the chief factor affective speed of sound in air as pressure and density change in lockstepGeneral formula for speed of sound in dry air General formula for ideal gases and air https://en.wikipedia.org/wiki/Soundhttps://en.wikipedia.org/wiki/Speed_of_soundc velocity of soundv temperature in ⁰C  At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn)c velocity of sound, ϒ adiabatic index/heat capacity ratio/Laplace coefficient, densityR Molar/Universal Gas Constant (8.314 J/K-mol), T absolute temperature (K), M molar mass of the gask Boltzmann constant (1.38*10-23 J/K), m mass of single molecule c velocity of soundT temperature in K  15

16. Speed of Sound in SolidsSound in solids can have different speeds depending upon the deformation mode Volumetric Deformations (compression)—P-wavesShear Deformations (shearing)—S-wavesTypically Pressure waves travel faster in materials than do shear wavesSpeed of sound for stiff materials is sometimes given for long rods or one-dimensional solidshttps://en.wikipedia.org/wiki/Speed_of_soundhttps://en.wikipedia.org/wiki/Speed_of_sound#Equations16

17. Speed of Sound in LiquidsThere are no shear deformations in fluids, so there is only compression/pressure wavesSpeed depends upon pressure/depth, temperature, and composition (i.e. salinity for sea water)—other effects are minorSpeed of sound for fresh water, is ~1481 m/s at 20 °Chttps://en.wikipedia.org/wiki/Speed_of_soundhttps://en.wikipedia.org/wiki/Speed_of_sound#EquationsSpeed of Sound vs Depth (Pacific Ocean seawater)17

18. HomeworkPut all the various formulas for speed of sound for gas, liquid, solid and plasma in your binder.Find what Mach Number and a Sonic Boom are and add to your binderFind tables for density, adiabatic index/heat capacity ratio/Laplace coefficient, bulk modulus, etc. so you can calculate speed of sound for most materials—focusing on air, water, and steel first.Also find at least one table with speeds of sound of general materialsWe will check these at the binder check for next class18