double slit experiment

• equipment

  • laser
  • souble slit
  • white screen
  • metre ruler
• method

  • set up apparatus in partially darkened labaratory
  • measure slit separation with vernier callipers
  • adjust so distance between slit and screen is 0.5m
  • measure across large number of fringes using ruler and divide by number of fringe widths to find fringe width
  • increase distance by 0.1m and repeat increasing by 0.1m until 1.5m
  • repeat experiment twice more and record mean width for each distance
• graphs and calculations

  • plot a graph of width against distance
  • draw a line of best fit
  • wavelength = gradient x slit separation
  • $w=$$\frac{\lambda D}{s}\ \rightarrow\ \lambda=$$\frac{ws}{D}=$$Gs$
  • G is the gradient
• safety

  • laser in eyes is dangerous

  precaution

  • keep away from eyes
• improvements

  • ensure screen and double slit are aligned perfectly normal to the laser
  • avoids parallax error in measurement of fringe width
  • use a set square and ruler to reduce measuring error