L24 傳輸波 Travelling Waves

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Pre-Amble

http://freewallsource.com/img/2014/9/ocean-waves-wallpaper-16832-17547-hd-wallpapers.jpg

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')

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) v_r: speed of receiver wrt medium; +ve (-ve) for receiver moving towards (away from) the source v_s: 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) (103-1: end slide 23; 104-1: end slide 55 108-1 to end)

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)

Supporting Simulations

Wave on a String

Rotation-Oscillation
Waves On String

Sound

Sound Waves
and Doppler

Doppler Shift Demonstrator

家 / 教學 / 物理 baixiaoming AT gmail.com