Absorption spectroscopy refers to a wide range of techniques where one measures how much light of a particular wavelength (color) is absorbed by a sample. Since color can often be correlated with the presence and or structure of a particular chemical, and since absorbance is often an easy and cheap measurement to make, absorbance spectroscopy is widely used for for both qualitative (is a chemical present) and quantitative (how much) and structural (is it degraded) work in a wide range of fields. For instance, DNA absorbs light in the UV range (which is partly why sunlight is dangerous) so the amount of DNA in a sample can be determined by measuring the absorbance of UV light.