Fourier-transform spectroscopy

Imagine you have a toy that can make music when you press a button on it. The toy makes a sound that has a pitch, just like when someone sings or plays an instrument. You can hear the pitch of the sound, but you don't know what makes that sound or how it does it.

Now, imagine you have a special machine that can take the music sound and break it into tiny little pieces. You can't see these pieces, but the machine can tell you how many of them there are and how long they are. The machine can also use this information to put the pieces back together to make the sound again.

This machine is like a Fourier Transform Spectrometer. It takes light waves and breaks them into tiny little pieces. Just like with the toy, you can't see the pieces, but the machine can tell you how many there are and how long they are. Instead of using this information to put the pieces back together to make a sound, the Fourier Transform Spectrometer uses it to tell you what the light is made of.

Different materials and substances absorb and reflect light waves in different ways. When light passes through something, it loses some of its original "shape" as it interacts with the particles in the material. This changes the way it appears to the Fourier Transform Spectrometer. The Fourier Transform Spectrometer reads the tiny changes in the light waves and uses them to tell you what the materials are made of.

So, just like the toy that makes music and the special machine that breaks it into pieces, the Fourier Transform Spectrometer takes light and breaks it into tiny pieces to tell you what materials are in it.