Question

What is spectroscopy?

Answer 1

The interaction of light with matter.......

Explanation:

The chemist is usually faced with two questions....

`i.` `"What is it?"`

`ii.` `"How much of it is in the sample?"`

And, usually, all forms of spectroscopy tries to answer these questions, directly or indirectly, by shining light (or part of the electromagnetic spectrum) on the sample, and interpreting the response. The most direct method of spectroscopy is X-ray crystallography which uses X-rays, and employs high frequency radiation to determine the structure of a molecule. Lower frequency radiation, UV, and IR, can examine transitions within a molecule. Here a few links to older questions on this subject.

https://socratic.org/questions/what-type-of-transition-is-examined-by-nmr-spectroscopy-what-type-of-transition-?source=search

https://socratic.org/questions/what-are-the-advantages-and-disadvantages-of-uv-ir-nmr-and-raman-spectroscopies?source=search

https://socratic.org/questions/how-is-ir-spectroscopy-interpreted

In all these cases, some idea of how much of the sample is present can be gained from the intensity of the signal.......and this addresses question (ii).