The Michelson-Morley Interferometer

• What is the name of the interferometer developed by Michelson and Morley?

  Michelson-Morley Interferometer
• What was the luminiferous aether proposed to be?

  A medium for light waves
• Who developed the wave theory of light?

  Christiaan Huygens
• Why did physicists assume light traveled through a medium?

  All known waves traveled through a medium
• What did Huygens call the medium for light waves?

  Luminiferous aether
• What was the aim of the Michelson-Morley experiment?

  To prove the existence of the aether

  
• In what year did Hippolyte Fizeau measure the speed of light in moving water?

  1849
• How did Fizeau measure the speed of light?

  By using light beams in moving water
• What did Fizeau find about light moving with and against the current?

  Light moving with the current was faster
• What was the aether wind?

  The motion of the aether against light
• What was predicted about light traveling into the aether wind?

  It would travel slower than perpendicular light
• What does absolute motion refer to?

  Motion measured relative to the aether
• How could the phase difference in light beams determine Earth's motion?

  By measuring the phase difference caused by speed changes
• What did the Michelson-Morley interferometer consist of?

  Two arms at right angles with mirrors
• What role did the beam splitter play in the interferometer?

  It created two coherent light beams
• Why was a plane of glass used in the interferometer?

  To ensure equal travel distances for beams
• What was the purpose of the mercury bath in the interferometer setup?

  To allow rotation with minimal friction
• What was the predicted phase shift when the interferometer was rotated?

  0.4 times the width of one fringe
• What did Michelson and Morley observe in their experiment?

  Displacements around 0.02 fringe widths
• What conclusion did scientists draw from the null result of the experiment?

  The aether does not exist
• What does it mean that the speed of light is invariant?

  It remains unchanged by Earth's motion
• What is the implication of no medium for measuring Earth's motion?

  No absolute motion exists
• What is the setup and function of the Michelson-Morley interferometer?

  • Two arms at right angles
  • Mirrors at each end
  • Beam splitter at intersection
  • Forms two coherent light beams
  • Measures phase difference to detect motion

  
• What were the steps and predictions of the Michelson-Morley experiment?

  1. Light beams split and travel different paths
  2. Expected phase shift due to aether wind
  3. Predicted shift: 0.4 fringe widths
  4. Actual results: 0.02 fringe widths
  5. Conclusion: Aether does not exist

  
• What are the key conclusions from the Michelson-Morley experiment?

  • Aether does not exist
  • Speed of light is invariant
  • No absolute motion can be measured