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The Michelson Interferometer

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The Michelson Interferometer

  1. 1. Physics 101 THE MICHELSON INTERFEROMETER
  2. 2.  Electromagnetic waves interfere with each other in the same way as mechanical waves:  Waves with the same frequency will interfere constructively when in phase and destructively when out of phase.  Lasers produce light that is monochromatic (single wavelength) and coherent (same phase).  The phase difference required for complete destructive interference on waves with equal intensity, frequency and polarization is described by a fraction of a wavelenght  λ/2 = π rad = 180’ INTRODUCTION
  3. 3.  The purpose of the Michelson Interferometer experiment is to produce interference fringes by splitting a beam of light.  A beam of light is split by a silvered plate, one on the half- beams strikes a fixed mirror, and the other a movable mirror.  The beams are brought back together and an interference pattern is produced. This is due to the phase change caused by the altered path length by the movable mirror.  Moving a mirror ½ a wavelength changes the phase of half beam by one wavelength. THE EXPERIMENT (Hyperphysics)
  4. 4.  By adjusting the movable mirror the wavelength is changed and different path lengths are produced.  Constructive interference (intensity maximum) is given by: m λ = 2d  The Michelson Interferometer can be used to make distance measurements by moving the mirror and counting the interference fringes which move by a reference point. ( Hyperphysics)  The distance d associated with m fringes is given by: d= m λ / 2 APPLICATIONS
  5. 5.  “The fringes for wavelengths λ = 632.8 nm and 420 nm are shown above. As the magnitude of the path difference increases the fringes move outward while as the magnitude of the path difference decreases the fringes move inward.” (fp.optics) UNDERSTANDING THE CONCEPT (fp.optics)
  6. 6.  You are studying different lasers in your physics tutorial. You are told that the beam of light produces 480 fringes in a distance of .33 mm. Find the wavelength  Using m λ = 2d  2 d = 480 λ λ = 0.66 mm/480 λ = 1.375 µm = 1290 nm IN THE LAB
  7. 7.  This time you are given a laser and told its wavelength is 376nm. Your lab partner manages to count 534 fringes. What is the distance?  Using m λ = 2d  Convert 576nm to 0.00576  0.00534 (376) = 2 d  d= 2.00784/2  d= 1.000392 IN THE LAB
  8. 8.  http://hyperphysics.phy- astr.gsu.edu/hbase/phyopt/michel.html#c1  http://fp.optics.arizona.edu/jcwyant/JoseDiaz/MichelsonInter ferometerFringes.htm SOURCES

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