Determining the Velocity of Light by Means of the Rotating-Mirror Method According to Foucault and Michelson - Measuring the Image Shift as a Function of the Rotational Speed of the Mirror

Once the rotary mirror is turning at a high frequency ν, the shift Δx of the image on the scale is observed. In the period

which the light requires to travel to the rotary mirror and back to the end mirror, the rotary mirror turns by the angle

Thus, the image shift is

The velocity of light can then be calculated as

To determine the velocity of light, it is sufficient to measure the shift in the image at the maximum speed of the mirror, which is known (P5.6.1.2). Measuring the image shift as a function of the speed supplies more precise results (P5.6.1.1).

1	476 40	Rotary mirror
1	471 830	He-Ne Laser, linearly polarised
1	463 20	Front-silvered mirror
1	460 12	Lens in frame, f=5 m
1	471 88	Beam splitter
1	460 22	Holder with spring clips
1	311 09	Glass scale, 5 cm
1	521 40	Variable transformer, 0...250 V
1	575 214	Oscilloscope 30 MHz, two-channel, analogous
1	559 921	Semiconductor detector
1	501 02	BNC cable, 1 m
1	501 10	BNC adapter, straight
1	300 41	Stand rod, 25 cm, 12 mm Ø
1	300 42	Stand rod, 47 cm, 12 mm diam.
1	300 44	Stand rod, 100 cm, 12 mm diam.
1	300 01	Stand base, V-shaped, large
4	300 02	Stand base, V-shaped, small
1	300 11	Saddle base
2	301 01	Leybold multiclamp
1	301 09	Bosshead S
1	311 02	Metal rule, 1 m

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