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Unformatted text preview: as great as it was, was actually an underestimate. The true speed of light is just a half a smidgeon under 3 ∙ 108 m/s, which is about 186,300 miles per second! We call this speed c. c = 2.9979 × 108 m/s ≈ 3 × 108 m/s Historical Background (cont.)
• Roemer’s main contribution was proving that the speed of light is finite. Since Roemer, several people contributed to determining the precise value for c. In 1849 Louis Fizeau found an excellent approximation for c without resorting to astronomical means. He used a rapidly rotating, toothed wheel. He shined a beam of light through one opening between the teeth, which reflected off a mirror over 5 miles away. When the wheel spun fairly slowly, the light could easily pass through the opening, reflect, and pass through it again in the other direction before its path was blocked by the next tooth of the wheel. By making the wheel spin faster and faster until the reflected beam of light was blocked, Fizeau was able to calculate c. • JeanBernard Foucault also made accurate measurements of c. He shined l...
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This note was uploaded on 11/17/2011 for the course PHYS 121 taught by Professor Burgeson during the Fall '11 term at BYU.
- Fall '11