What is Spectroscopy and How Does it Work?

When a material is heated it emits light that is characteristic of the atomic/molecular makeup of the material and its temperature. Spectroscopy is the science of measuring and interpreting this light across the entire electromagnetic spectrum.

Spectroscopes

A spectroscope is an instrument for separating light into its constituent wavelengths and corresponding intensities. This separation can be done in variety of ways, two common methods being the use of a diffraction grating or a prism. Check out this interactive on the wave properties of light.

Light Refraction Through a Prism

A prism operates using the principles of refraction. For visible light, blue light is refracted (bent) through a larger angle than red light when incident (not head on) onto a glass-like surface. When the glass is in the shape of a prism, this spreads out the light as shown above. The colors of the visible spectrum, called the elementary colors, are red, orange, yellow, green, blue, indigo, and violet (in that order). Check out this web interactive on how a prism works.

Diffraction is a phenomenon by which waves are distorted in the neighborhood of obstacles. A diffraction grating is a collection of reflecting (or transmitting) elements separated by a distance comparable to the wavelength of the light under study. By a process of wave interference (both constructive and destructive), the grating is able to separate light into its constituent wavelengths. Diffraction gratings allow more precise measurements than prisms. Check out these interactives on diffraction. Single slit diffraction and Diffraction from a grating

Light Diffraction Through a Diffraction Grating

A spectrometer is the complete instrument allowing the separation of light into its constituent components and the quantitative measurement of the spectrum’s intensity. These devices can become quite sophisticated!

The Spectrometer