Waves Flashcards
Progressive wave
A wave that transfers energy without transferring material and is made up of particles of a medium oscillating
Amplitude
A wave’s maximum displacement from the equilibrium position
Frequency
The number of complete oscillations passing through a point per second
Wavelength
The length of one whole oscillation
Speed
The distance travelled by the wave per unit time
Phase
The position of a certain point on a wave cycle
Phase difference
How much a particle/wave lags behind another particle/wave
Period
Time taken for one full oscillation
What happens when 2 points on a wave are in phase?
Two points on a wave are in phase if they are both at the same point of the wave cycle, they will have the same displacement and velocity and their phase difference will be a multiple of 360 degrees. They do not need the same amplitude, only the same frequency and wavelength.
What happens when 2 points on a wave are completely out of phase?
Two points on a wave are completely out of phase when they’re an odd integer of half cycles apart
Transverse waves
Oscillation of particles is at right angles to the direction of energy transfer e.g. EM waves which travel at 3x10^8 ms^-1
Longitudinal waves
Oscillation of particles is parallel to the direction of energy transfer
Polarised waves
A polarised wave oscillates only in one plane and only transverse waves can be polarised. Polaroid sunglasses are an application of polarisation.
Superposition
Superposition is where the displacements of two waves are combined as they pass each other, the resultant displacement is the vector sum of each wave’s displacement.
Constructive interference
Constructive interference occurs when 2 waves have displacement in the same direction
Destructive interference
Destructive interference occurs when one waves has positive displacement and the other has negative displacement, if the waves have equal but opposite displacements, total destructive interference occurs.
Stationary wave
A stationary wave is formed from the superposition of 2 progressive waves, travelling in opposite directions in the same plane, with the same frequency, wavelength and amplitude. No energy is transferred by a stationary wave.
Antinodes
Where the waves meet in phase, constructive interference occurs so antinodes are formed, which are regions of maximum amplitude.
Nodes
Where the waves meet completely out of phase, destructive interference occurs and nodes are formed, which are regions of no displacement
Path difference
The difference in the distance travelled by two waves
Coherent light source
A coherent light source has the same frequency and wavelength and a fixed phase difference.
