Post on 13-Dec-2015
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
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