Interference and Diffraction

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Interference and Diffraction
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What the Bleep? Video Clip

• http//www.livevideo.com/video/ConspiracyCentral/2
  AA3B5B73DB743B986904537C3A38EE1/what-the-bleep-the
  -double-s.aspx

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Diffraction

• When light passes through an opening that is
  large compared to its wavelength, it casts a
  sharp shadow.
• When light passes through an opening that is
  small compared to its wavelength, it casts a
  fuzzy shadow.

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• Diffraction any bending of a wave by means
  other than reflection or refraction.
• Light travels through a narrow opening to reveal
  an interference pattern
• Ex Diffraction glasses, CDs

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Youngs Interference Experiment

• When 2 beams of light are directed through two
  closely spaced slits, they produce fringes of
  brightness and darkness on a screen.
• The brightness was due to constructive
  interference.
• The darkness was due to destructive interference.

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Double-Slit Diffraction Applet

• http//surendranath.tripod.com/Applets/Optics/Slit
  s/DoubleSlitID/DblSltIntDifApplet.html

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Check Your Understanding

• Destructive interference results in what type of
  fringes, light or dark?
• Dark, because destructive interference cancels
  out wave amplitude, resulting in less light.
• Why does an interference pattern seem to repeat
  itself?
• B/c light is a wave (a transverse wave), and
  waves periodically repeat themselves.