Make Your Own Spectroscope

In this video I uploaded to Youtube, I show you how to make your own spectroscope using the SpectraSnapp app on your iPhone.  A spectroscope is an instrument which can analyze the various colors that make up white light, or any other light source, by diffracting the visible light into its constituent wavelengths, ROYGBIV — red, orange, yellow, green, blue, indigo and violet. The SpectraSnapp app is available for free at the iTunes store. SpectraSnapp is only available for the iPhone.

To make your own spectroscope, you need the following materials:

  • iPhone
  • free SpectraSnapp app available in the iTunes store
  • Diffraction grating (1000 lines per mm)
  • black construction paper
  • black electrical tape.

First of all, download Spectrasnapp from the iTunes store.

Now, to build the spectroscope.  Cut a 1 cm x 1 cm piece of diffraction grating and tape over the lens of your iPhone using the black electrical tape, so just one very narrow slit is exposed to light.  You will make a tube to direct the light into your iPhone out of black construction paper. Roll up the construction paper into a tube and tape down with the black tape.  Cut one end of the tube to be diagonal and one flat.  To the flat end, apply two more pieces of electrical tape, much like you did over the diffraction grating on the lens of the iPhone, so that only a very narrow slit is exposed to the light source.  Tape the diagonal end down to the iPhone, so that no ambient light is allowed in.  You have now made your spectroscope.

Point the end of your spectroscope to a light source, adjust the tube so you see the light spectra, which is a combination of the various atomic spectra which provide the light source, through your camera app, and take a picture.  Once you’ve taken a picture of the atomic spectra with your spectroscope, go to the SpectraSnapp app, and open the “Snapp” menu item.  Choose the spectra from your camera roll and bring it into the app.   Calibrate the spectra, which means rotating it and cropping it,  so that it is lined up with the atomic spectra within the “Analyze” menu item.

Once it is lined up, select apply and return to the “Analyze” menu.  Compare your spectra with the many sample atomic spectra provided by the app to identify the elements in the light source.

Remember, atoms have unique atomic spectra because the energy difference between their energy levels differs with each atom.  When an electron absorbs energy, it gets excited and goes from one lower energy level to a higher energy level.  When it relaxes back to a lower energy level, it emits the amount of energy equivalent to the distance between the energy levels in the form of light, whose frequency and wavelength is determined by the amount of energy given off.

The best way to learn to build your own spectroscope is to watch the Youtube video.  There are also instructions on how to build a spectroscope with the SpectraSnapp app.  Thank you to the folks at the American Physics Society, APS, for making the SpectraSnapp app available to all of us.