Waves Section 2

Waves Section 2

1. Superposition & Coherence

   • Superposition - happens when 2 or more waves pass through each other
     • When 2 waves are out of phase there are quiet paths
   • Constructive Interference
     • A crest plus a crest create a bigger crest
     • When oscillations are in phase
   • Destructive Interference
     • A crest plus a trough of equal sizes gives nothing
     • The 2 displacements cancel out each other, leaving silence
     • Happens when oscillations are 180* out of phase
   • 2 sources are coherent if they have the same λ, frequency and fixed phase difference
   • When the 2 waves cross-over this creates constructive interference increasing sound

2. Stationary Waves

   • Progressive waves reflected at a boundary can create stationary waves
   • Stationary wave = superposition of 2 waves with same F moving in opposite directions
   • No energy is transmitted
   • Nodes are where the amplitude of the vibration is 0
   • Antinodes are where the vibration is at a maximum amplitude

3. Diffraction

   • Amount of Diffraction depends on the wavelength
   • When the gap is > than wavelength, diffraction is unnoticeable
   • Get most diffraction when gap is same size as wavelength
   • If the gap is smaller then they are mostly reflected
   • Waves superimpose to create differences in intensity

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