SpeedofLight

# SpeedofLight - THE SPEED OF LIGHT Introduction According to...

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1 THE SPEED OF LIGHT Introduction According to Einstein’s Principle of Relativity the speed of light in a vacuum has the same value, c = 3.00 x 10 8 m/s, in all inertial reference frames, regardless of the velocity of the observer or the velocity of the source emitting the light. Prior to Einstein’s special theory of relativity there had been a great deal of time and effort invested in measuring changes in the speed of light to confirm the ‘ether theory’. Although the Michelson- Morley Experiment proved that there was no ‘ether’, the result had far reaching consequences; it indirectly confirmed Einstein’s Principle of Relativity. In this experiment light is timed as it travels over a known distance. A light beam is initially reflected from a rotating mirror to a fixed mirror, where it reflects back to the rotating mirror. When the light beam returns to the rotating mirror, this mirror will be in a slightly different orientation. As a result the returning beam will reflect from this mirror along a slightly different line that the initial beam of light had. Measurement of the angle between these two beams of light is used to time the trip back and forth and thus obtain a numerical value for the speed of light. Equipment ( see following page ) high speed rotating mirror optics bench couplers fixed mirror 1 lens (48 mm FL) measuring microscope 1 lens (252 mm FL) 0.5 mW He-Ne laser 2 calibrated polarizers one-meter optics bench 3 component holders laser alignment bench 2 alignment jigs tape measure

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2 Theory The light beam from a laser is focused by lens L 1 to form a point image at h. The beam then passes through a beam splitter, another lens L
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## This note was uploaded on 09/02/2011 for the course PHYS 4D taught by Professor Luna during the Spring '11 term at DeAnza College.

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SpeedofLight - THE SPEED OF LIGHT Introduction According to...

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