Wave profile:__wavelength ( l ), time period ( T ), phase relationship ( f ) - { between particles => time interval between particle maximums (y-axis) - as a fraction of period T. }

Phase changes on reflection: wave reflected at boundary going into denser medium ( v_dense < v₁ ), or phase change at barrier is 1/2 a wavelength on reflection.

- Predicts future position of a wavefront. Principle - "every point on a wavefront can be regarded as a source of secondary, spherical wavelets and the new wavefront will be the surface which touches all secondary wavelets."

- When 2 waves meet they produce disturbances at the points where they overlap, this is called superposition (as a resultant vector).

____ ____

Interference - 2 periodic waves of equal frequency & amplitude meet at a point. The resultant disturbance µ phase difference.
Disturbance in phase = 2 x individual waves (constructive interference)
Disturbance out of phase (180°) = zero resultant (destructive interference)
Phase difference depends on : 1) initial phase of both waves. 2) path difference - the distances travelled by the 2 waves.

Beat frequency, ____f₁ > f₂

A stationary wave is produced when 2 progressive waves (= frequency, amplitude) travelling in opposite directions overlap. This can be demonstrated from the resultant of 2 wave trains passing over each other.

_______

Table - Stationary vs Progressive Waves