Lecture series for Conceptual Physics, 8th Ed'

1
A wiggle in time. p324
Sound needs a medium.
Light does not need a medium.
Lecture series for Conceptual Physics, 8th Ed.
2
Vibration of a Pendulum p325
Tp
2?
L/g
Depends on length of string and gravity.
Fig 18.1 In all cases, the motions are
independent of mass.
To and fro motion is called-
Note Sliding not rolling.
Simple Harmonic Motion
Pendulum dribbling sand makes a sine wave.
3
Crest
Trough
The mass bobbing up and down on a spring exhibits
simple harmonic motion.
Frequency is the number of cycles per second.
(Hz)
Period is the number of seconds per cycle. (Tp)
1
Frequency
Period
4
Waaavvee Moottionnn p328
Energy is transferred from source to receiver.
Light and water waves molecules of medium shake
back and forth along wave path.
These are transverse waves. p 329
5
Wave Speed p328
Wave speed wavelength x frequency
v ?
f
Longitudinal Waves p330
Longitudinal (SOUND waves).
Transverse
6
Interference p331
Destructive
Constructive
Recall noise canceling headsets.
7
Standing Waves p332
Figure 18.13 The incident and reflected waves
interfere to produce a standing wave.
8
Doppler Effect p333
Stationary bug standing on water produces
concentric waves.
When the bug moves to the right, it makes new
circles. Each circle starts where the bug stepped.
Longer wavelengths.
Shorter wavelengths
9
Bow Waves p335
Now, bug is going faster than wave speed. Its
stepping ahead of one wave to make the next.
Fig 18-18 Wave pattern made by a bug swimming at
wave speed.
10
Shock Waves p336
The overlapping waves produce a sharp pressure
increase.
The shock wave, sonic boom, follows the plane.
11
Sounds Waves
The tuning fork is the wiggle in time.
The sound waves move to the right.
The molecules move to the right and then back to
the left, returning to their original spot.
The energy of the sound travels forward at the
speed of sound, but each air molecule only
oscillates back and forth along the direction
that the wave is going.
This type of motion is called LONGITUDINAL
12
Refraction of Sound p346
Refraction mean bending.
Sound travels faster in warm air than in cold air.
The faster moving portion of the wave goes
ahead.
The wave changes direction as a portion of it
goes ahead.
13
Resonance p349
14
Interference p350
15
More interference fig 19-15
Constructive interference
Destructive interference
What you hear here.
Beats p353
f262Hz
f264Hz
f266Hz
The wahwahwah sound, the beats, has a
frequency of 4Hz.
Sounds like the end.