Tomsk State University. Physical Department.
Laboratory of training physics experiment
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Doppler  Effect  Обратно  Далее  
In 1969 we managed to make measurements of longitudinal Doppler effect in an optical range. We reproduced the method Fabry and Buisson measurements who had analyzed the light of fast-rotating paper disk through the Fabry-Perot etalon. Nowadays there is an opportunity of using laser light 532.8 nm. A slight mirror tilt enables to get that the laser emits a single mode that allows using high-resolution etalon with spaces up to 15 cm and even 50 cm.
When the motor rotation frequency was 17,000 rpm, the disk edge speed was 180 m/sec that gave the ratio v/c=6 10-7. By long distances between the mirrors the diameters of the interference rings were becoming smaller so that they were to be examined in telescope. The laser light was going perpendicularly to the rotating disk, and the light scattered on-the-mitre 12° was focused on the etalon through the lens. Here are the photos of interference rings by motionless disk (Photo 1) and rotating disk (Photo 2).  
Using a small mirror we succeeded in directing the light scattered in opposite direction to the etalon additionally. On the photo 4 below there are split rings being obtained from the beams scattered in opposite directions by rotating disk. Gradual motor speed acceleration leads to diameters increasing in one rings system and diameters decreasing in the other rings system. Under speed 153 – 163 m/sec the rings overlap was visible to the eye quite well. With the help of the telescope the pattern was being observed interactive. By different methods of measurement an error had been in the range from 0.5 to 3.3%.  
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