Waves and Sound - Kaplan Physics Ch. 7 Flashcards
What is a general wave characteristic involving transfer of energy?
Waves will allow transfer of energy from one point to another w/o transfer of matter.
Define Tranverse Waves and name an example.
Transverse waves: particles move (oscillate) in the direction that is perpendicular to the direction of the wave (wave propagation).
Examples: Light wave, Water wave, Electromagnetic Wave
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This is the normal wave that you think of! Think: tying a string to a door then wiggling it.
If the wave is moving to the right, then the oscillation is up and down.
Define Longitudinal Waves and name an example.
Longitudinal Waves: Particles move (oscillate) in the direction parellel to the direction of the wave (wave propagation.
If the wave is moving to the right, the oscillation is to the right too.
This is the funky looking wave. Think: a slinky.
Define Equillibrium Position
The point at which waves move around.
Define Crest/Trough
Maximum/Minimum point of a wave (respectively)
Define Displacement (x)
How far point is from equilibrium position. Vector Quantity.
Define Amplitude (A) and its units.
Definition: Area of maximum displacement from equilibrium position.
Units: Dependent on wave; Meters for water, Pascals for sound.
Define Wavelength (ƛ) and its units.
Definition: Distance from one crest to another.
Units: Meters (m)
Identify the relationship between amplitude and energy.
High amplitude = more energy
Identify the relationship between wavelength and frequency.
Low wavelength = High Frequency
Define frequency (f), its units, and formula.
Definition: Number of wavelengths passing a certain point per second.
Units: Hertz (Hz) = 1 cycle/s (cps)
Formula: f = 1/T
where T is period.
Cycles per second
Define Period (T), its units, formula.
Definition: Number of seconds for wavelength. to pass certain point.
Units: seconds (s)
Formula: T = 1/f
Seconds per cycle
Identify the relationship between period (T) and frequency (f).
They are the inverse of each other.
This should help you remember the two formulas. T =1/f & f = 1/T
Define angular frequency (ω), its units, formula.
Definition: Measures how oscillation speed.
Units: radians per second
Formula: ω = 2 π f = [(2π)/T]
Measures how fast a waves crests/troughs cycle.
Define wave speed/propagation speed (v), its units, formula.
Definition: How fast wave travels through medium.
Units: Meters per second (m/s)
Formula: v = f * ƛ
Define phase when considering waves.
Definition: A phase is a pont in a wave cycle.
Define what in phase/out phase. Include relative phase difference.
In phase: When 2 waves have the same displacement and motion at a given point. (AKA, their crest/troughs line up).
Phase Difference will be 0.
Out phase: When crest of one wave lines up with the trough of another.
Phase Difference will be half of wave (Ex. ƛ/2 OR 180º)
Phase difference measured in degrees (º) or radians.
What does the Principle of Superposition state?
Waves overlap in space. Can be calculated by adding displacements.
Formula: ytotal = y1 + y2
With formula, you are essentially adding the sum of indv. displacements.
Define Constructive Interference and states it’s impact on a wave’s energy/amplitude.
Definition: Describes when two waves are in-phase.
Impact on energy: Higher energy bc of larger amplitude.
THINK: How 2 sound waves will produce louder sound.
Define Destructive Interference and state its impact on a waves energy/amplitude.
Definition: Describes when two waves are out-of-phase.
Impact on energy/amplitude: Waves will have smaller amplitude or complete cancelation. Less energy.
THINK: How noise canceling headphones work.
Imagine tying a string to a door:
Define Traveling Waves and how it works.
Definition: Wave which moves in specific direction w/o interuption. No interuption = shape of wave has constant repeating pattern through time.
How it works: Incident wave is the original wave produced, once this wave reaches the bound end, it will reverse and a reflected wave will return.
For ex. Sound waves through air OR ocean waves
Define Standing Waves and how it works.
When two traveling waves moving in opposite directions interfere with each other so that the total wave appears still.
When considering standing waves,
Define Node and provide general example of where it can be found.
Definition: Area on wave in which amplitude is 0. (Wave is at rest/no fluctuation is displacement).
General Example: Closed boundries which don’t allow oscillation.
Specific ex. closed end of pipe/secured end of string
When considering standing waves,
Define Antinode and provide general example of where it can be found.
Definition: Areas on wave which fluctuate.
General Example: Open boundries which allow maximum oscillation.
Specific ex. open end of pipe/free end of string
