What is a spectroscopy

See below.

Explanation:

By definition,

Spectroscopy is the study of various absorption and emission spectra of various elements.

In spectroscopy, we tend to analyse and study the atomic spectra which are formed by irradiating atoms with say, alpha particles.

In case of an absorption spectrum, the atom absorbs the energy of a wave (concerned with a specific wavelength) and reachs an "excited state". The remaining waves hit a zinc sulphide plate and we see a spectrum forming.

In case of an emission spectrum, the "excited state" atom release radiation, which hits the plate and we see a spectrum forming.