Waves/Sounds Flashcards
What is Pulse?
A single vibratory disturbance in a medium
What happens when a pulse travels down a string with velocity?
Energy is transferred to the string, which causes segments to vibrate up and down; creates an illusion of a continuous path
What is the equation for the velocity of a pulse?
v=sqrt[T/(m/L)]
v=sqrt(TL/m)
What do waves transfer?
Waves ONLY transfer energy
What is the Principle of Superposition?
When two pulses at the same point and at the same time interact, the interaction produces a single pulse whose amplitude is equal to the sum of the displacement of the original two pulses
What happens after the interaction of two pulses?
Both pulses continue in their original directions of motion, unaffected by the interaction
What is Interference?
Superposition of waves of identical or opposite phases to produce constructive or destructive interference, respectively
What is Constructive Interference?
When two pulses of identical phases (upward or downward) interact, creating a displacement larger than the original two; amplitudes add together
What is Destructive Interference?
When two pulses with opposite phases (upward and downward) interact, creating a displacement smaller than the original two; amplitudes subtract
In destructive interference, what happens when the two pulses have the same amplitude?
The interaction can cause the pulses to momentarily cancel out
What is a Series of Waves?
Continuous up and down vibration given to a string that results in sets of transverse pulses; also known as a wave train
Pertaining to waves, what is Frequency?
Number of waves per second (f)
Pertaining to waves, what is Period?
Time required to complete one wave cycle (T)
What is a Phase?
Relative position of a point on a wave with respect to another point on the same wave
What does it mean for two waves to be “in phase”?
The two waves have the same frequency at the same point in time with no phase difference
What is a Wave Length?
Distance between any two successive points (crest or trough) in phase; λ or lambda
What is a Crest?
Peaks of a wave
What is a Trough?
Valleys of a wave
What is Amplitude?
Maximum displacement from rest position
What is the equation for the velocity of a transverse wave?
v=fλ
For sound, what does the amplitude of the wave represent?
Intensity or volume
For sound, what does the frequency of the wave represent?
Pitch
At the same amplitude, waves with higher frequencies transmit __________ energy per second.
More
What is a Mechanical Wave?
Waves that result from the vibration of a physical medium (ie. drum, string, water); can be transverse or longitudinal
What is a Longitudinal Wave?
A wave with regions of compressions and expansions that appear to travel parallel to the disturbances; also known as a compressional wave
What is an example of a longitudinal wave?
Sound
What is a Transverse Wave?
A wave that contains a vibration that travels perpendicular to the apparent direction of motion; equation: v=fλ
What is a Standing Wave?
A wave in which incident and reflected waves combine to produce a wave that appears to be “standing” in one place
What are Nodal Points?
Points that segment a standing wave; corresponds to points where no appreciable displacement takes place
What is the Fundamental Mode of a wave?
First mode of a standing wave; easiest frequency mode of vibration possible; l=λ/2; contains zero nodal points
As the nodes of a standing wave increase, what happens to its wave length?
Increases by λ/2
1 node= λ, 2 nodes= 3λ/2, etc.
What is Resonance?
Buildup of wave energy due to constructive interference of standing waves; maximum transfer of energy from one body to another that shares the same natural vibrating frequency
What is an Acoustical Wave?
Longitudinal wave in matter
What are Beats?
When two sound waves interfere; the regions of constructive and destructive interference
What is Frequency Difference?
Beats per second
What is Path-Length Difference?
Something interference is dependent on; determines when interference is constructive or destructive
What is the path-length difference of a constructive interference?
L1-L2=nλ; whole multiples (ie. 2, 4, 6)
What is the path-length difference of a destructive interference?
L1-L2=(n+1/2)λ; odd multiples (ie. 1.5, 2.9, 3.4)
What is Diffraction?
When a wave encounters a boundary, the wave appears to bend around the corner of the boundary; creates the illusion of waves bending
What is the Doppler Effect?
As sound approaches a point, pitch (frequency) increases; when sound passes a point, pitch (frequency) decreases
