Waves definitions Flashcards
Dsplacement
The distance moved from equilibrium for a point on a wave
Amplitude
The maximum displacement from the equilibrium position
Wavelength
The minimum distance between two points oscillating in phase, for example the distance between one peak to the next. The length of one complete wave cycle, in metres.
Period
The time taken for one complete wavelength to pass a given point OR the time taken to complete one oscillation. Measured in seconds.
Frequency
The number of wavelength cycles passing a given point per unit time (seconds), measured in Hertz (1 Hz = 1s-1)
f = 1/T where f = frequency (in Hz) and T = time period (in seconds)
Progressive Wave
Transfer of energy as the result of oscillations of the medium through which the energy is travelling
Longitudinal wave
The oscillation of particles is parallel to the direction of travel of the wave e.g. sound
Transverse wave
The oscillation of particles is perpendicular to the direction of travel of the wave e.g. waves on a string, electromagnetic
Mechanical wave
Energy is transferred through a medium (i.e. by the oscillations of particles)
Phase
The position of an oscillating particle or field at a given time on a wave cycle, expressed in degrees or radians, where 1 full wave cycle = 360 degrees or 2π radians.
Wave speed
The distance travelled by the wave per unit time
Reflection
When a wave rebounds from hitting a boundary between two mediums
Refraction
When a wave changes direction as it enters a new medium, due to a change in the speed of travel
Intensity
The radiant power transferred per unit area (intensity = power / area). Measured in W m-2. Intensity is proportional to amplitude2
Electromagnetic waves
Waves that travel by oscillation of the electromagnetic field. Electromagnetic waves are transverse waves
Plane polarised wave
A transverse wave in which the oscillations are limited to only one plane
Critical angle
The angle of incidence at the boundary between two media that will produce an angle of refraction of 90 degrees
Total internal reflection
The reflection of all light back into the original medium when hitting a boundary between two media; the original medium will have a higher refractive index and the incidence angle at the boundary must be greater than the critical angle.
Principle of superposition
When two or more waves meet at a point, they interfere and the resultant displacement is the vector sum of the individual displacements
Coherence
When two or more waves or wave sources have a constant phase difference and the same frequency
Phase difference
The difference in position on a wave cycle at a given time between two oscillating points, either on the same or different waves, expressed in degrees or radians, where 1 full wave cycle = 360 degrees or 2π radians
Path difference
The difference in the distance travelled by two waves from their source to a specific point
Constructive interference
When two or more waves that are in phase superpose and create a maximum (which is a greater amplitude than any of the individual amplitudes)
Destructive interference
When two or more waves that are in antiphase, superpose and create a minimum (the resulting amplitude is smaller than any of the individual amplitudes)
Note: destructive interference does not necessarily result in zero amplitude; two waves with different amplitudes can interfere destructively and the resulting wave will have a non-zero amplitude
Diffraction
The spreading of a wave after passing through a gap or around an obstacle
