The resultant displacement at a point at a given time is the algebraic (vector) sum of the displacements of each wave at that point at that time
Constructive Interference
When two waves meet in Phase they produce a wave of greater amplitude
Destructive Interference
When two waves meet exactly out of phase they produce a wave of smaller amplitude (zero if the amplitude of the waves were the same)
Coherent sources
Produce waves of the same wavelength or frequency and be in phase or have a constant phase difference between them
Standing waves
Produced by the interference of two waves, of the same type and having the same wavelength moving in opposite directions and meeting
Diffraction
The spreading out of waves when they meet an obstacle or aperture (gap)
Diffraction grating
A rectangular piece of glass treated on one side to make it opaque and then scored on the opaque side to produce parallel lines of equal width and equal separation
