Young

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Topics

• Youngs double slit experiment with laser light
  Determine the wavelength of the laser light.
• The double slit experiment with white light
  Determine the coherence length of white light.

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Interference and Coherence Length

• The path length difference must be less than the
  coherence length of the light. Otherwise no
  definite phase relationship exists and the
  interference pattern is not visible.
• No problem for laser light (coherence length of
  order or meters).
• White light has much shorter coherence length ?
  Interference pattern only visible for small m.

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V I.A. Youngs Double Slit Experiment with Laser
Light
Screen
Large Screen (to keep laser light within your
area)
Double Slit
Laser

• Vary slit separation and observe changes.
• Measure interference maxima spacing and determine
  the wavelength of the laser from it.

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V I.B Youngs Double Slit Experiment with White
Light
Diffuser
Double Slit
Incandescent Light

• The double slit interference pattern (if there)
  will appear when looking against the direction of
  light propagation through the diffuser.
• Try different slit widths.
• Estimate coherence length of white light.

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V I.B Youngs Double Slit Experiment with White
Light
Diffuser
Double Slit
Photometer aperture
Incandescent Light

• Use the photometer aperture to only let light
  through one slit.
• Observe and explain.