Chapter 19: Vibrations and Waves Flashcards
A vibration is
A periodic wiggle in time
A periodic wiggle in both space and time is
A wave
A wave extends from
One place to another
Light is
An electromagnetic wave that needs no medium
Sound is
A mechanical wave that needs a medium
If we suspends a stone at the end of a piece of string, we have a
Simple pendulum
The period of the pendulum depends only on the
Length of the pendulum
The longer the length of a pendulum, the longer the
Period
Just as the higher you drop a ball, the longer it takes to
Reach the ground
A wave is pictorially represented by a
Sine curve
A sine curve is
Obtained when you trace out the path of a vibrating pendulum over time
When a bob vibrates up and down, a marking pen traces out a sine curve on the paper that
Moves horizontally at constant speed
Vibration and wave characteristics
1) Crest
2) Troughs
Crest
High points of the wave
Troughs
Low points of the wave
Amplitude
Distance from the midpoint to the crest or to the trough
Wavelength
Distance from the top of one crest to the top of the next crest, or distance between successive identical parts of the wave
How frequently a vibration occurs is called the
Frequency
The unit for frequency is
Hertz (Hz) after Heinrich Hertz
A frequency of 1 Hz is
A vibration that occurs once each second
Short wavelength
High frequency and high energy
Long wavelength
Low frequency and low energy
Frequency
1) Specifies the number of to and fro vibration in a given time
2) Number of waves passing any point per second
Period is
Time to complete one vibration and inversely proportional to frequency
Wave motion
Waves transport energy and not matter
Two common types of waves
1) Longitudinal wave
2) Transverse wave
Two differences wave because of
The direction the medium vibrates compared with the direction of travel
Longitudinal wave
Medium vibrates parallel to direction of energy transfer
Backward and forward movement consist of
1) Compression (wave compressed)
2) Rarefractions (stretched region between compressions)
Transverse wave
Medium vibrates perpendicularly to direction of energy transfer up and down movement
The distance between adjacent peaks in the direction of travel for a transverse wave is its
Wavelength
The vibrations along a transverse wave move in a direction
Perpendicular to the wave
The wavelength of a longitudinal wave is the distance between
Successive compressions and rarefactions
Wave speed describes
How fast a disturbance moves through a medium
Wave speed related to
Frequency, period, and wavelength of a wave
Wave interference occurs when
Two or more waves interact with each other because they occur in the same place at the same time
Superposition principle: The displacement due the interference of wave is
Determined by adding the disturbances produced by each wave
Constructive interference
1) Crest of one wave overlaps the crest of another
2) Individual effects add together to produce a wave of increased amplitude
Destructive interference
1) Crest of one wave overlaps the trough of another
2) High part of one wave fills the low part of another
3) Individual effects are reduced or even canceled out
Superposition principle amplitude were
Adding and subtracting
Interference pattern made when
Two vibrating objects touch the surface of water
Regions where a crest of one wave overlaps the trough of
Another produce regions of zero amplitude
Point along these regions, wave arrive
Out of phase with each other
Sound wave - louder sound is the result of the
Principle of resonance
Resonance is caused by the fact that the sound waves reflected from
The closed end of the tube return to the top and reinforce the waves from the tuning fork and constructive interference
The wave interference tie a rope to a wall and shake the free
End up and down to produce a train of waves
Wave are reflected back
Along the rope
By shaking the rope just right, we can cause the incident and reflected waves to form a
Standing waves - combination of two waves moving in opposite directions
Nodes
Regions of minimal or zero displacement with minimal or zero energy
Antinodes
Regions of maximum displacement and maximum energy
Antinodes and nodes occur
Equally apart from each other
Doopler effect
Change in frequency due to motion of the source
If observer or source moves toward each other, wave frequency is
Increasing
If observer or source moves away from each other, wave frequency is
Decreasing
Higher and lower frequency were equally to
Higher and lower pitch sound
Light blue shift
Increase in light frequency toward the blue end of the visible spectrum
Light red shift
Decrease in light frequency toward the red end of the visible spectrum
The star and planet orbit their
Center of mass
Spectral lines move toward the red as the start travels
Away from us
Spectral lines move toward the blue as the start travels
Toward to us
Wave barrier: wave superimpose directly on top of
One another producing a wall
Supersonic
Aircraft flying faster than the speed of sound
Bow wave
V-shaped form of overlapping waves when object travels faster than wave speed
An increase in speed will produce a narrower V-shape of
Overlapping waves
Shock wave
Pattern of overlapping spheres that form a cone from objects traveling faster than the speed of sound
Shock waves consists of two cones
1) A high-pressure cone
2) A low-pressure cone
A high pressure cone generated at the bow of the
Supersonic aircraft
A low pressure cone that follows toward (or at) the tail of
The craft
Sonic boom sharp cracking sound generated by
A supersonic aircraft
Sonic boom intensity due to
Overpressure and under pressure of atmospheric pressure between the two cones of the shock waves
