General Wave Behavior Physics of Music, Spring 2014.
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Transcript of General Wave Behavior Physics of Music, Spring 2014.
General Wave Behavior
Physics of Music, Spring 2014
Key Termstraveling wave
transverse wave
longitudinal wave
plane waves
circular waves
Huygen's principle
reflection
diffraction
velocity
frequency
wavelength
What is a traveling wave?A disturbance which travels through a medium, transmitting energy from the source to the observer without any net transfer of mass.
Animation courtesy of Dr. Dan Russell, Kettering University
Transverse WaveTransverse: displacement is perpendicular to direction of wave propagation
Spring image source: http://www.factmonster.com/dk/science/encyclopedia/energy-waves.htmlAnimation courtesy of Dr. Dan Russell, Kettering University
Longitudinal Wave
Longitudinal: displacement is parallel to direction of wave propagation.
Animation courtesy of Dr. Dan Russell, Kettering UniversityLong. Spring image source: http://www.factmonster.com/dk/science/encyclopedia/energy-waves.html
Plane waves and Circular Waves
Plane circular (diffraction!)
Image sources:(top) Berg and Stork, Physics of Sound, 3rd ed.(bottom) UC Irvine Optics research group.
Circular Plane
Huygen’s PrincipleA wavefront can be thought of as being composed by a large number of “wavelets”, each of which spread out spherically in time and space.
Image source: Berg and Stork, Physics of Sound, 3rd ed.
Law of reflectionAngle of incidence equals angle of reflection.
qi = qr
Both angles are measured with respect to the normal(dashed line perpendicular to the surface)
Image sources:http://www.dl.ket.org/physics/companion/thepc/compan/Light/Light-t.htm
http://www.worsleyschool.net/science/files/reflectionlaw/page.html
Plane Wave Reflection and Ray Diagrams
normal
Ray diagram
Image source: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reflec2.html#c1
Reflection from concave surface
Image source: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reflec2.html#c1 (left); Berg and Stork, Physics of Sound, 3rd ed. (right)
Applications of Reflection?
Image source: D. Hall, Musical Acoustics (left)
DiffractionTendency for waves to spread out as a result of passing by an edge (barrier or passing through a slit)
Image source: http://innovativescience.blogspot.com/2011/02/diffraction.html
Narrow aperture
Wide aperture
Diffraction PatternsDiffraction in ripple tank
Diffraction on a MUCH larger scale.
Image sources: (top) http://scripts.mit.edu/~tsg/www/demo.php?letnum=Q%201&show=1Bottom: http://www.suntrek.org/factary/d.shtml
Diffraction in Action
Key TermsWave Mechanics: Part II
traveling wave
transverse wave
longitudinal wave
plane waves
circular waves
Huygen's principle
reflection
diffraction
velocity
frequency
wavelength
A Day at the Beach
Check out the plane waves!!!
Travelling Wavesx
Animation courtesy of Dr. Dan Russell, Kettering University
Wavelength (l): spatial distance from crest-to-crest
Frequency (f): how many times per second one particular point oscillates
lf Physical Parameters
[m/s] : velocity How far a wavefront travels per unit time, Dx/Dt. Property of the medium/material.
T [s]: period How much time elapses between generation of each pulse (wavefront)
f [Hz]: frequencyHow many oscillations per second at one point in space, f = 1/T.
l [m] = wavelengthHow far between two crests or two troughs
𝑣t = to
t = to+ Tl
Travelling waves in ripple tank: high speed video (240 fps)
Image from Arbor ScientificRipple tank image, oblique view
Speed of Sound in Various Bulk Media
Material Speed of Sound [m/s]
Air (20 C) 343
Brass 3475
Sea Water 1533
Wood ~ 3600
Data from: http://www.engineeringtoolbox.com/sound-speed-solids-d_713.html