Waves and Quantum Behaviour Flashcards
Superposition
When 2 waves pass through each other, the total displacement at a point is equal to the vector sum of the individual displacements at that point.
Constructive interference
When 2 waves that are IN PHASE - phase difference of 0deg (360deg) or 0 (2pi) meet, the waves reinforce each other. A maximum is observed. When path difference is a whole number of wave lengths, n(lamda)
Destructive interference
When 2 waves that are in ANTI PHASE - phase difference of 180deg or pi meet, the waves cancel each other out. A minimum is observed. When path difference is an odd multiple of half a wavelength: ((2n+1)/2)(lamda) or (n + 0.5)(lamda) Unless the amplitudes are exactly equal, the cancelling effect won’t be complete
Interference patterns
Provided the waves are coherent (have a constant phase difference) a stable interference pattern is observed
Ray
A line we draw perpendicular to the wavefront. It shows the direction of travel of the wave
Wavefront
A line or surface on which all points of the wave are IN PHASE
Amplitude
Maximum displacement from the undisturbed position
Time period
Time to complete 1 cycle or oscillation
Wave length
Distance between 2 adjacent points that are IN PHASE
Frequency
Number of cycles or oscillations per second. Number of wave crests passing a point per second
Wave equation
v=f(lamda)
Speed of sound in air
330 ms^-1
Speed of light
3.0x10^8 ms^-1
Phasor
A rotating arrow that represents a wave
Coherent
Sources are coherent if they have the same wavelength and frequency and a fixed phase difference between them
‘General’ wave equation
y=Asin(2.pi.f.t) where y is vertical displacement, A is amplitude, f is frequency and t is time passed. Can also be written as y=Asin(wt) where w is angular velocity
Angular velocity
Also called angular frequency. w=2.pi.f