This exercise is intended to familiarize you with the identification of functional groups in organic compounds using infrared spectra. Before you can use this technique, you need to have an introduction to infrared spectroscopy and to what an IR spectrum is.
Infrared spectroscopy deals with the interaction of infrared light with matter.
The energy of an infrared photon can be calculated using the Planck energy relation. This shows that high energy photons have high frequency. You can see that both frequency and wavenumber are directly proportional to energy. Molecules are flexible, moving collections of atoms. The atoms in a molecule are constantly oscillating around average positions.