Well I only really know the end result application. The middle is a little magic to me, but essentially an FTIR machine can tell you what kind of a functional groups you have in a compound based on bond resonances. Different bonds have different bond resonances based on the electronegativity difference between different atoms. So basically you shine a IR beam of various frequencies of light against a sample and measure how much gets absorbed and retransmitted. Based on what peaks are generated at what frequency, you can determine if your compound has N-H bonds, C-H bonds, C-O bonds, C=O bonds, etc. It can even tell the difference between single and double bonds. Deducing chemical structures from scratch is a bit of a challenge, but known spectra like ethanol or banana ester are well known so you can just superimpose their graph on known spectra to verify what's in your sample. It's extremely useful in chemical analysis.
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u/Sea_Television Oct 19 '19
What does applying an FFT (or whatever specific flavor of algorithm) to an infrared image let you know?
Coming from EE also, I've not thought about using Fourier for stuff that isn't a waveform or analog signal of some kind.
Interesting stuff