Waves Flashcards
(28 cards)
Amplitude
The magnitude of the maximum displacement of the medium
Antinode
Position of maximum amplitude on a standing wave
Coherence
Two sources of waves are coherent if there is a constant phase difference between them
Constructive interference
Occurs when multiple sources tend to superpose to increase the amplitude of a wave at a given point.
For two source interference this occurs with a path difference of n
Destructive interference
Occurs when multiple sources tend to superpose to decrease the amplitude of a wave at a given point (often to zero).
For two source interference this occurs with a path difference of (n+0.5)
Diffraction
The spreading out of a wavefront when it passes through a gap.
Max. diffraction when wavelength is similar to gap width
Some diffraction when wavelength is smaller than gap width
No diffraction when wavelength is larger than gap width
Displacement
The distance and direction of a point in the medium from its equilibrium position
Frequency
The number of complete waves passing a point per unit time or
The number of oscillations completed by a point in the medium per unit time
Fundamental mode of vibration
The lowest frequency (longest wavelength) standing wave oscillation that a system can support
Harmonics
Oscillations with frequencies that are integer multiples of the fundamental frequency of a system. The first harmonic is thus another name for the fundamental
Intensity
Power per cross sectional unit area.
It is proportional to the amplitude² of a wave
Interference
The phenomenon which may occur when two or more waves of the same type are incident upon the same point, resulting in a wave of different amplitude from the original waves
Longitudinal wave
Wave in which the direction of vibration is parallel to the direction of energy transfer
Malus’ law
For plane-polarised light incident on a polarizing filter, the transmitted intensity is given by:
I=Iocos²θ,
where Io is the incident intensity and theta is the angle between the plane of polarisation and the angle of the filter
Node
Position of zero amplitude on a standing wave
Path difference
The difference in path length measured from a wave source to a given point and path length measured from a second wave source to the same point
Period
The time for one complete oscillation of a particle in the medium
Phase
How ‘far through’ an oscillation a point on the wave is, from 0 to 360° or from 0 to 2π radians
Phase difference
Relates to oscillation of two points on the same wave
How far ‘out of step’ one oscillation is from the other
Plane-polarised
A wave in which the oscillations of the medium occur in a single plane. It is only possible to polarise transverse waves
Principle of superposition
When two or more waves meet at a point
the resultant displacement is given by the vector sum of the individual displacements of the waves
Progressive wave
Wave that transfers energy from one place to another as a result of oscillations
Reflection
A wave ‘bounces’ off a surface formed by the boundary between two different media. The angle of incidence is equal to the angle of reflection
Refraction
A wave changes speed in traversing the boundary between two different media. This leads to a change in wavelength (always) and a change in direction (unless the wave is propagating along the normal to the boundary)
