Chapter 30: Reflection and Refraction
The nature of light
Speed of light (in vacuum)
c = 2.99792458 x 10
8
m/s
measured but it is now the definition
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Michelson’s 1878 Rotating Mirror Experiment
Picture credit
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German American physicist A.A. Michelson realized, on putting together
Foucault’s apparatus, that he could redesign it for much greater accuracy.
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Instead of Foucault's 60 feet to the far mirror, Michelson used 2,000 feet..
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Using this method, Michelson was able to calculate
c = 299,792 km/s
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20 times more accurate than Foucault
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Accepted as the most accurate measurement of c for the next 40 years.