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Define Interference
Interference: When two or more waves are superimposed on each other, they will combine to form a single resultant wave
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Name two things the amplitude of the resultant wave will depend on
- The amplitudes of the individual combining waves
- How these waves travel relative to each other
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Superposition Principle
Superposition principle: When two or more waves are simultaneously present at a single point in space, the displacement of the medium at that point is the sum of the displacements due to each individual wave.
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If waves interfere constructively, the waves are in ______ with each other (explain). The _______ add causing a _____ _____ _____
- phase (crest meets crest, trough meets trough)
- amplitudes add
- larger resulting wave
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If the waves interfere destructively, the waves are exactly _____ _____ _____ with each other (explain). Crest of one wave coincides with the ______ of the other waves and vice versa. Their amplitudes _______, causing a _____ _____ _____
- out of phase (or 180° or π radians out of phase)
- trough
- subtract
- smaller amplitude wave
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Explain what happens in each of these scenarios. (both 5-story)
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a) The pulses have the same ______ but different _______
b) When the pulses overlap, the _____ function is the sum of the individual _____ functions.
c) When the pulses no longer overlap, they have not been permanently affected by the _______
State which is constructive or destructive
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Assume two waves with the same amplitude, frequency and wavelength, traveling in opposite directions in a medium. State the formula for DR and DL
They interfere according to the _______ _______
- DR = asin(kx - ωt)
- DL = asin(kx + ωt)
- superposition principle
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Label the standing wave(s) and the traveling wave(s)
Standing wave patterns produced at various times by two waves of equal amplitude traveling in ________ directions
State the snapshot time (in terms of the period) based on the features of the waves
What is the formula for the resultant wave?
This is the wave function of a _______ ______. There is NO ________ term, and therefore it is NOT a ______ _____
- blue and green are traveling waves and brown is the standing wave
- opposite directions
- D = (2asinkx)cosωt
- standing wave
- (kx - ωt)
- traveling wave
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In observing a standing wave, there is no sense of motion in the direction of propagation of either of the ______ _____
original waves
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D = (2asinkx)cosωt
A node occurs at a point of _____ amplitude at all times, i.e. sinkx = ____ or kx = ____
These correspond to positions of x where
x = ___, ___, ___, ___,... = ___
where n = ___, ___, ___, ___...
- zero amplitude
- sinkx = 0 or kx = nπ
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An antinode occurs at a point of ______ ________ (=2a), i.e. sinkx = ____ or kx = ____. What are the corresponding positions of x and n?
- maximum displacement (=2a)
- sinkx = ±1
- kx = nπ/2
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Distance between adjacent antinodes is ____. Distance between adjacent nodes is _____.
Distance between a node and an adjacent antinode is ____.
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The amplitude of the vertical oscillation of the string depends on the _______ position of the element. Each element ______ within the confines of the envelope function ________.
Label the diagram
- horizontal position
- vibrates
- 2Asinkx
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Label the different scenarios
A wave ______ when it encounters a discontinuity.
a) The discontinuity is where the wave speed _______. Which direction will have the faster wave speed?
b) The discontinuity is where the wave speed _______. The reflected pulse is ________
A wave ______ when it encounters a boundary
c) The reflected pulse is _______ and its amplitude is _______
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Consider a string fixed at both ends with length L. Standing waves are set up by a continuous ________ of waves incident on and reflected from the ends. There is a boundary condition on the waves
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The ends of the strings must necessarily be _____. They are fixed and therefore must have _____ displacement. The boundary condition results in the string having a set of ______ ______ of vibration. Each mode has a characteristic _______.
- nodes
- zero
- normal modes
- frequency
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The normal modes of oscillation for the string can be described by imposing the requirements that the ends be _____. The nodes and antinodes are separated by ____
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This is the first normal mode that is consistent with the boundary conditions.
It has ______ at both ends
One ______ is in the middle
This is the _______ wavelength mode
What is the formula for L and λ 1
- nodes
- antinode
- longest wavelength
- L = λ1/2 or λ1 = 2L
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Consecutive normal modes add an antinode at each step.
The second mode corresponds to λ = ___
The third mode corresponds to λ = ___
In general: λ n = ____
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For standing waves on a string, state the formula for fn (3)
State the formula for the lowest frequency:
f1 = ____
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The frequencies of the remaining normal modes are integer multiples of the _______ frequency. Frequencies of normal modes that exhibit such an integer multiple relationship form a ______ series, and the normal modes are _______. The fundamental frequency f1 is the frequency of the first harmonic, the frequency fn = ____ is the frequency of the nth harmonic, where n is the _______ ________
- fundamental
- harmonic series
- harmonics
- fn = nf1
- harmonic number
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State the formula for:
f1 and λ1
fn and λn (2)
v
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Nodes and antinodes are spaced equally.
Each loop (node to node) equivalent to ____
Nodes and antinodes are separated by ____
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