Four Chapter 1

• Use a series of pictures produced at regular intervals as in a movie film.
• Use a stroboscope in conjunction with a camera (shutter held open).
• A disk with slits in it may be spun in front of your field of view to measure short times.
  • Use the stroboscope to stop periodic motion.
  • If slit frequency = the frequency of the motion, then through the slits we see the motion in the same position each time,
  • by knowing
    • rotation speed
    • # of slits

frequency can be calculated.

• To ensure the disk is rotating at the correct frequency, follow these steps.
  • Rotate the disk with increasing speed until the object is stopped in more than one place.
  • Now reduce the speed until the object is stopped in one place only.
  • Determine the rotational frequency of the strobe.
  • Determine the frequency of the object by using the formula:

• In the above formula, f stands for frequency.
• Similarly, a stroboscopic light can be used to stop the image of an object.

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October 28, 2013