The SpectraSnapp app comes with directions to build a simple spectrometer that fits over the phone’s camera. All that is required is a tube made out of construction paper, with a thin diffraction grating at the end. The grating, available online for less than a dollar, breaks the light apart into its component wavelengths, which the camera sees as a series of colored lines.

“You can determine through our app what the light source you’re pointing the camera at is made out of,” Roche said.

Different light sources produce different spectral signatures, depending on their chemical composition. The spectrometer lets users see that white light given off by different types of bulbs is a combination of different emission lines. A fluorescent bulb will have a different series of lines than a sodium light, while an incandescent bulb emits a continuous spectrum. The app comes with a spectral library of twenty of the most common light sources, which the team anticipates expanding as the app becomes widely used.