A way of visualizing the Nyquist theorem is in terms or periodic sampling of the second hand of a clock that makes one revolution around the clock every 60 seconds. The Nyquist sampling rate here...

A way of visualizing the Nyquist
theorem is in terms or periodic sampling of the second hand of a clock that
makes one revolution around the clock every 60 seconds. The Nyquist sampling
rate here should correspond to two samples per cycle, that is, sampling should
be done at least every 30 seconds. (a)Supposewebeginsamplingwhenthesecondhandisat12o’clockandthatwesample
the clock every 15 seconds. Draw the sequence of observations that result. Does
the second hand appear to move forward? (b) Now suppose we sample every
30 seconds. Does the second hand appear to move forward or backward? What if we
sample every 29 seconds? (c) Explain why a sinusoid should be sample data
little more than twice its frequency. (d)Now suppose that we sample every
45 seconds. What is the sequence of observations of the second hand? (e)
Motion pictures are made by taking a photograph 24 times a second. Use
part (c) to explain why car wheels in movies often appear to spin backward
while the cars are moving forward!