# I Can a Spectrometer be used to detect material type?

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1. Jun 3, 2017

### jjoll

Hi,
I dont know much about science of spectrometry, but I am working on a project where i need to detect and differentiate between different types of material types, and I was just wondering if I can use an Spectrometer such as Desktop Spectrometry Kit v3 ( https://publiclab.myshopify.com/products/desktop-spectrometry-kit-3-0?variant=7183158980) to distinguish and detect different material types. For example to distinguish glass object from metal, plastic and paper object.

thanks

Last edited by a moderator: Jun 3, 2017
2. Jun 3, 2017

### Staff: Mentor

Distinguishing between different materials is the usual application of spectrometry. Covering classes as large as all plastics could be challenging, but it is certainly possible.

3. Jun 3, 2017

For a spectrometer that works in the visible, one experiment that could prove interesting is to measure the reflection spectrum of paper that is colored with different colors of crayons or paints. $\\$ For the kind of identification you asked about in the OP, it could be somewhat difficult to assess what a given material happens to be without having a high quality sample such as a pane of glass or lucite and running a transmission spectrum. In some cases, these materials are highly transparent in the visible and a transmission spectrum might not tell you very much. $\\$ An additional idea would be to test the reflectance spectrum of various metals. Silver is highly reflective throughout the entire visible, while gold absorbs significantly at the shorter wavelengths in the visible and doesn't become highly reflective until around 6500 Angstroms=thereby the gold color. I think you would find a similar result for copper. $\\$ And one additional thing you might get some good results with is measuring the transmission spectrum of various optical filters. Some are made of different types of glasses, while others are interference filters made from layers of thin films (usually deposited on a transparent substrate). The former are usually much less expensive than the latter. In any case, you might get some interesting results with transmission spectra of various filters. An optical filter typically transmits a selected band of wavelengths and blocks out other wavelengths. $\\$ Note: In a transmission spectrum, you run a spectrum of a broadband source plus sample. (Call that $V_s(\lambda)$). You then run a spectrum without the sample, (Call that $V_{cal}(\lambda)).$ The transmission at wavelength $\lambda$ is given by $\tau(\lambda)=\frac{V_s(\lambda)}{V_{cal}(\lambda) }$