Waves

• A progressive wave is an oscillation that travels through matter, transferring energy but not transferring matter
• Phase difference is the difference in the displacement of particles along a wave measured in radians.
• all progressive waves can be reflected, refracted and diffracted
• reflection occurs when a wave changes direction at a boundary between two media
• refraction occurs when a wave changes direction as it changes speed when it enters a new medium
• diffraction is the spreading out of a wave as it passes through a gap.
• Polarisation is unique to transverse waves, When an oscillation of a wave is restricted to one plane only, the wave is plane polarised.
• Intensity is directly proportional to amplitude^2
• Typical wavelengths

  • Radio - 10^3
  • Micro - 10^-2
  • Infrared - 10^-5
  • Visible - 0.5x10^-6
  • Ultraviolet - 10^-8
  • X-ray - 10^-10
  • Gamma - 10^-12
• n (refractive index) = c (speed of light) / v (speed of light in medium)
• Total internal reflection occurs at a boundary with no refraction. The angle of incident must be above critical angle.

  sinC = 1/n
• The principle of superposition states when two waves meet at a point, the resultant displacement of the wave at that point is equal to the sum of the displacements of the individual waves.
• Coherent waves are waves with constant phase difference.
• Stationary waves form when two progressive waves travel in opposite directions and superpose
• Nodes - zero amplitude

  Antinodes - maximum amplitude