Jun 6, 2012

Cell Phone Spectroscopy

My phone and a spectrometer (your school probably has some in the chem. lab)

Secondary teachers have been waging the cell phone battle for the better part of the last decade now. Most of us are frustrated that students choose to be entertained by that little device rather than be educated by our instruction. Or, as I've heard it somewhere: we can't come to grips that a 3-inch screen is more captivating than a lecture.

My plan of attack is to use cell phones for good, so to speak, and fold them into the instruction. What I've found is that if the student is using the phone for science he cannot also be using it for any other purpose. Most importantly, I've found that students actually enjoy using their technology as a tool in the science classroom. 

Here's a great little lesson that I've found is quite engaging.

Required Materials

Smartphone with camera (preferably one per student)
Spectroscope (most high schools have these somewhere, get a bulk set )
) Various light sources (noble gas tubes, fluorescent lights, incandescent lights, and an LED will give a nice set of results)

Making Your Own Spectroscope

NASA has a nice link on how to make your own spectroscope if you want to be really cheap. (how to make one yourself). Of course you'll need some diffraction gatings


Point the spectroscope toward a light source (slit towards the light). For best results, be sure that no other light source is on (you don't want to gather photons from several sources if you are trying to determine the spectrum of a particular source). Hold the cellphone's camera flush against the diffraction grating (leaving a gap produces bad results; try it, you'll see quite readily this is true). When you have a nice set of spectral lines, take a picture.

fluorescent lights
Our kitchen's fluorescent lights
ambient sunlight
Ambient sunlight

What I love about this

Most high school physics teachers have done a lab with the spectrometers (actually, if you haven't you should probably look over your required standards - you're most likely missing something) but it is often tedious for students to hold the spectral tube toward the light and observe the various colors. Students will say "yeah I see the lines, but it's hard to tell what colors are there." If you've done this lab, you know what I'm talking about. With the cellphone you can capture a still photo and analyze it 'til the cows come home.

So there you have it - this isn't anything fancy, and it's not a complete lab in itself - but methinks this is quite the supplement to your existing spectroscopy unit.

A note about the phone...

My Phone - you don't need one this fancy for this to work...
 The phone I'm using in this demo is a Galaxy Nexus, a very new "smartphone",  but even my student's most "basic" camera phones can do this task with ease. So don't feel like you need the best and the most expensive to pull this off. 

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