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Science Experiments -   Stroboscopic Effect

Often it is necessary to measure the rate at which objects rotate. An instrument which is capable of doing this is called a stroboscope. Stroboscopes give flashes of bright light. This light is then made to fall on the rotating object. The rate at which the stroboscope flashes light is then adjusted so that the light falling on the rotating object appears to be stationery. At this point of time the frequency of flashing of the stroboscope is the same as that of rotation of the object. In this way the rate of rotation of rotating objects can be determined.

Let us now undertake a simple experiment to demonstrate this concept.

 You Will Need A white cardboard disc, about  4" - 5" in diameter A hand drill A nail
 Procedure Take a cardboard disc and divide it into eight equal pie shaped sections.  Colour alternate sections red so that you have four white and four red sections. Now pierce the nail through the exact centre of the disc. The nail should be firmly attached to the disc and turning the nail should turn the disc. Open the chuck of the hand drill by rotating the screw and insert the other end of the nail in the chuck. Tighten the chuck so that the nail is firmly gripped by the chuck Rotate the handle of the chuck. At first the disc will appear to be moving backward, as you increase the speed a point will come where the disc appears to be perfectly still. If you further increase the speed the disc will appear to be moving rapidly forward. This experiment demonstrates the stroboscopic effect.