Superposition, interference, diffraction

• Principle of Superposition


  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
• Monochromatic


  A single wavelength