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These four Mathcad documents illustrate different
aspects of the Fourier transform. They explore the source
of the Nyquist frequency and the dependence of the
resolution of the spectrum on sampling. In FTIntro.mcd,
students achieve a qualitative understanding of the Fourier
transform through experimentation with graphic representations of
data and their transforms. In Part 1 of FTIntro.mcd,
students sample a continuous function and learn how aliasing can
occur; in Part 2, a vector of a more complex waveform
illustrates that the frequencies contained in the waveform
appear as spectral lines in the transform. Exercises permit
further exploration of the Nyquist frequency and illustrate the
relationship of resolution to number of samples. At the end,
the students perform an integral transform of the same
waveform. The second document, FT2IR.mcd, demonstrates how
spectral information is coded in an interferogram and how
the interferometric data limits resolution in the spectrum.
In FT2IR.mcd, the inverse FT is used to generate an
interferogram from a spectrum with two notches representing
absorption. The third document, FT3Pulse.mcd, demonstrates
that a short sample of a wave must contain a range of
frequencies. In the fourth document, FT4FreeIndDecay.mcd,
free induction decay (FID) and its Fourier transform are
explored and related to NMR signal analysis. The entire set of
documents contains many student exercises and hands-on
activities for learning the concepts presented.
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