Pre-Amble
耶和華在高處大有能力,勝過諸水的響聲,洋海的大浪。(Ps93#4)
好消息 News: Test Results for MS#3 (see previous lecture)
Homework: SHM (Bobble Heads )
The Link: Rotation → Oscillation → Waves
(PHeT )
What is a Wave? (15')
Your browser does not support the video tag.
Key Ideas
Wave Speed (≠ Speed of Particles in Medium)
$$ \, v_{w,string}= \sqrt { T_s \over \mu } \, $$
$$ \, v_{w,light} = \sqrt { 1 \over \mu \epsilon } = { c \over n } \, $$
$$ \, v_{w,sound} = \sqrt { K_s \over \rho } \, $$
Special Case: SHM → Sinusoidal Waves
$$ D(\vec r,t) = A \, \sin ( \,+ \vec k \cdot \vec r \, - \, \omega t \, + \, \phi_o ) \, (positive \, direction) \,$$
$$ D(\vec r,t) = A \, \sin ( \,+ \vec k \cdot \vec r \, + \, \omega t \, + \, \phi_o ) \, (negative \, direction) \,$$
$$ \, \lambda ={ v_{w} \over f } \,\,\,\, \, \omega = | k | \, v_{w} $$
$$ \, | k |= {2 \pi \over \lambda} \, $$
$$ \, \omega = { 2 \pi f } = { 2 \pi \over T } \, $$
Doppler Effect on Frequency (medium)
$$ \, {f_r} = \left ( {{ v+ v_r } \over {v - v_s}} \right ) {f_s} \, $$
v : speed of waves in the medium (equation above)
vr : speed of receiver wrt medium; +ve (-ve) for receiver moving towards (away from) the source
vs : speed of the source wrt medium; +ve (-ve) for source moving towards (away from) the receiver
EM/light (no medium):
Relativistic_Doppler_effect
ViewGraphs: Travelling Waves (Ref" Knight Chapter 16)
1D Wave Description (waves on strings)
wave speed (v)
Lateral (⊥) ↔ Longitudinal (∥)
Displacement D(x,t), Particle Velocity dD/dt(x=C,t)
Sinusoidal Waves
Nature of Sound & Light
2D and 3D Waves
Power and Intensity (decibels)
Doppler Effect (Introduce with Simulations)