Unit 6 Formula Sheet

Travelling Wave
V = f f = 1 / T
= 2 f k = 2 /
Vsound = 330 m/s in air at T = 0oC
Vsound = 343 m/s in air at T = 20oC
Vsound = 1450 m/s in water
String F = tension
= mass per unit length
Sound in Gases = cp / cv
kB = Boltzmann constant
T = temperature
m = molecular mass
Sound in Liquids Bad = adiabatic bulk modulus
= density
Sounds in Solids Y = Young's modulus
= density
Intensity of a wave, where A is amplitude Diffraction minima 
     
       Power
I = ---
       Area
Intensity definition sin = / D , where D is the width of the single slit opening. 
     P 
I = ---
    4r2
Intensity for spherically uniform radiation at distance r sin = 1.22 / D , where D is the diameter of a circular opening.
= 10 log ( I / Io ) Decibels (dB) if Io = 10-12 W/m2
fbeat = f1 - f2 Beat frequency
Doppler effect

 V = velocity of sound relative to transmitting medium
VO = velocity of observer relative to transmitting medium
VS = velocity of source relative to transmitting medium
                    + when moving toward each other.
VO and VS are:
                    - when moving apart.
f / f = Vrel / V Doppler effect for VO << V and VS << V
Vrel = relative velocity of source and observer
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