Topic 4: Waves and Oscillations Flashcards
Oscillation
A repeated back and forth motion.
Cycle
One complete oscillation.
Amplitude
The maximum displacement from the equilibrium position
Frequency
The number of oscillations completed in a second (unit is hertz, Hz)
Displacement
The distance of the oscillating object measured from its equilibrium position
Period
The time taken for an oscillation. f=1/T; T=1/f
Phase difference
Two oscillations which are not in step have a phase difference (expressed as an angle). A phase difference of one oscillation is 2pi radians.
Simple harmonic motion
A motion where the acceleration is proportional to the displacement at all times but is oppositely directed and towards equilibrium.
Damping
The loss of energy of oscillations due to work against (friction or viscous medium). Can be heavy, light or critical.
Results in reduction in amplitude
Natural frequency
The frequency at which a system will oscillate naturally.
Forced oscillations
Oscillations of a system which is being driven at another frequency than its natural one.
Resonance
When the driving oscillation has the same frequency as the natural frequency of the system, the amplitude of the system will increase.
Travelling wave
A disturbance moving from a source and transferring energy from one point to another.
Transverse wave
Where the direction of energy propagation is at right angles to the direction of travel of the wave.
Longitudinal wave
Where the direction of energy propagation is parallel to the direction of travel of the wave.
Wavefront
A line of surface which joins all points which have the same displacement at the same moment (they are all in phase).
Ray
A line at right angles to the wavefronts which shows the direction of energy travel of the wave.
Crest and trough
For a transverse water wave, the maximum and minimum displacements.
Compression & rarefaction
For a longitudinal wave, points of maximum and minimum density of the medium.
Wavelength
The distance between consecutive points on the wave which are in phase
Wave speed
The speed of travel of the energy of the wave.
Intensity
The rate of flow of energy through unit area perpendicular to the direction of travel of a wave. Unit: Wm-2
Snell’s Law
For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is also equal to the ratio of their speeds.
Diffraction
The spreading of waves when they pass through an opening or round an obstacle.
Superposition
When two waves pass the same point at the same time, their displacements are added together to calculate the resultant displacement.
Interference
Superposition of coherent sources resulting in an interference pattern.
Constructive/Destructive
Interference in which the resultant is reinforced/ cancelled.
