Oscillations and Waves Flashcards
Displacement
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Distance a particle moves in a particular direction from its mean (equilibrium) position
Amplitude
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Maximum displacement from the mean position
Frequency
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(f)
Number of oscillations per unit time
Period
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(T)
Time taken for one complete oscillation (cycle)
Phase difference
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Difference in phase between two points
Simple Harmonic Motion
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Motion that takes place when the acceleration of an object is proportional to its displacement from its equilibrium position and is always directed toward its equilibrium position
a=-w^2x
Damping
Involves a force that is always in the opposite direction to the direction of motion of the oscillating particle
Note: this force is a dissipative force
Critical Damping
When a resistive force is applied to an oscillating system that causes the particle to return to zero displacement in a min amount of time
Natural Frequency of Vibration
When a system is displaced from equilibrium and allowed to oscillate freely, it will do so at its natural frequency of vibration
Resonance
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A transfer of energy in which a system is subject to an oscillating force that matches the natural frequency of the system resulting in a large amplitude of vibration
Forced Oscillations
A system may be forced to oscillate at any given frequency by an outside driving force that is applied to it
Wave Pulse
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Single oscillation or disturbance in a medium
Continuos Progressive (Traveling) Wave
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A series of periodic pulses
Note:
Involves a transfer of energy, each point on the wave has the same amplitude
Transverse wave
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Wave in which the direction of motion of the energy transfer (wave) is perpendicular to the direction of motion of the particles of the medium
Note:
Light waves are transverse. Transverse waves cannot be propagated in gases
Longitudinal wave
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Wave in which the direction of motion of the energy transfer (wave) is parallel to the direction of motion of the particles of the medium
Note: Sound waves are longitudinal
Wavefront
Collection of neighbouring points on a wave that are in phase
Ray
Line drawn perpendicular to a wavefront indicating the direction of motion of the energy transfer
Crest
Top of a transverse wave
Trough
Bottom of a transverse wave
Compression
Area of high pressure in a longitudinal wave
Rarefraction
Area of low pressure (expansion) in a longitudinal wave
Wavelength
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Shortest distance along the wave between two points in phase with one another OR
distance traveled by wave in one period
Wave speed
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v
Speed of transfer of the energy of the wave
Intensity
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(I)
Power received per unit area
Note: For a wave, its intensity is proportional to the square of its amplitude
Law of Reflection
Angle of incidence is equal to the angle of reflection when both angles are measured with respect to the normal line
Snell’s Law
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Ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for a given frequency
Refractive Index
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(n)
a) ratio of the speed of the wave in the refracted medium to the speed of the wave in the incident medium
b) Ratio of the sine angle of incidence to the sine angle of refraction
Diffraction
Bending of a wave around an obstacle or spreading of a wave through an opening
Note: Diffraction is only noticeable when the size of the opening is smaller than or the same order of the size of the wavelength
Principle of Superposition
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When two waves meet, the resultant displacement is the vector sum of the displacements of the component waves
Constructive interference
Superposition of two waves which are in face with each other
Destructive interference
Superposition of two waves which are out of phase with each other
Path difference
Difference in the distances two waves must travel from their sources to a given point
Node
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Locations of constant complete destructive interference on a standing wave
Fundamental (first harmonic)
Lowest frequency mode of vibration of a standing wave
Standing (Stationary) wave
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Resultant wave formed when two waves of equal amplitude and frequency traveling in opposite directions in the same medium interfere
Note: Does not involve a transfer of energy, points on wave have varying amplitudes
Antinode
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Locations of maximum constructive interference on a standing wave
Doppler Effect
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Change of frequency of a wave due to the movement of the source or the observer relative to the medium of wave transmission
Resolution
Ability to distinguish between two sources of light
Rayleigh Criterion
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When the central maximum of one diffraction pattern overlaps the first minimum of a second diffraction pattern, the two sources are “just resolved”
Polarized light
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Light in which the electric field vector vibrates in one plane only
Brewster’s Law
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When light is incident on a surface at such an angle that the reflected and transmitted rays are perpendicular and the reflected ray is totally plane polarized, then the index of refraction of the substance is equal to the tangent of the angle of incidence (n=tan angle)
Analyzer
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Polarizer used to detect polarized light
Polarizer
device that produces plane polarized light from an unpolarized beam
Malu’s Law
The transmitted intensity of polarized light is equal to the product of the incident intensity times the square of the cosine of the angle between the direction of the analyzer and the direction of the electric field vibration of the polarized light (I=Iocos^2angle)
Optically Active Substance
One that rotates the plane of polarization of the light that passes through it OR one that changes the plane in which the electric field vector of the light vibrates
