Two-Source Interference

• Two-Source interference is easy to demonstrate in water or sound because they have measurable wavelengths

  you need coherent sources (frequency and wavelength have to be the same)

  its best to use the same oscillator for both sources
• demonstrating two-source interference for light is more difficult

  • you can either use two separate coherent light sources or shine a laser through two slits
  • the slits have to be around the same size as the wavelength so that it is diffracted
  • this gives a fringe pattern
• the fringes from diffraction are very small, so its difficult to get an accurate value of w

  • its easier to measure across several fringes and then divide by the number of fringe widths between