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Figure 5 shows the features of a Michelson-Morley interferometer - AQA - A-Level Physics - Question 3 - 2021 - Paper 7
Question 3
Figure 5 shows the features of a Michelson-Morley interferometer. Explain how, using this arrangement, Michelson and Morley attempted to detect the absolute motion ... show full transcript
Worked Solution & Example Answer:Figure 5 shows the features of a Michelson-Morley interferometer - AQA - A-Level Physics - Question 3 - 2021 - Paper 7
Step 1
outline the experimental procedure
Answer
The Michelson-Morley experiment utilized a beam splitter to divide a monochromatic light source into two beams. These beams traveled along perpendicular paths to mirrors M1 and M2, reflected back to the beam splitter, and then recombined. A telescope was used to observe interference patterns produced by the recombined beams. The experiment aimed to detect differences in the travel times of the light beams, which would indicate the motion of the Earth through the supposed ether.
Step 2
explain the expected result of the experiment
Answer
It was expected that if the Earth were moving through the ether, the light beam traveling in the direction of Earth's motion would take longer to return than the beam traveling perpendicular to that motion. This difference in travel times would cause a shift in the interference pattern observable through the telescope.
Step 3
describe the actual result and explain the significance of this result
Answer
The actual result of the Michelson-Morley experiment showed no significant interference shift, indicating no detectable difference in the travel times of the two light beams, regardless of the Earth's motion. This result was significant as it provided strong evidence against the existence of the ether, leading to the conclusion that the speed of light is invariant and that absolute motion does not exist, which later influenced the development of Einstein's theory of relativity.