I did this work in early October when I had some free time on the weekend. As a reminder, I was interested in how different colors of glow sticks spend their energy. I know, for example, that blue is an energetic color of light, and that red is a less energetic color of light. For a light source, giving off red visible light means that energy is being given off in small packets. Its like spending $100 just pennies at a time.
So I made a simple circuit just using a photoresistor inside a wooden box. I used an arduino to capture the readings and sent it to a Xively account, and later downloaded that information and plotted it (thanks Peter Oakes!). The Xively aspect of things was cool because I could see my experiment from anywhere in the world (even if I was only in the next room). I was hoping for a gspread library so I could use a Google Doc, but I think that will have to wait.
At any rate, my results are below:
As you can see, Green and Orange behaved very similarly. White, however, was always dim. On all accounts, I was shocked by how quickly they faded. I didn't expect it to be quite so exponential. The X-axis is in seconds, which means that in a matter of minutes, the light being given off is really diminishing. Green and orange have a sizeable difference in energy, so I was also surprised to see that they behaved so similarly. I, do however, know that the green color is easy to make with luminescent chemicals. Producing other colors often involves fluorescence. That is something with high energy emits light, which gets absorbed by something else and re-emitted as lower energy light. I think that might be the case here. Still I was surprised to see that this didn't lead to much dimming.
White should be a collection of a lot of colors, but not of lot of things give off white light as part of luminescence, so there is probably a lot of muting and filtering just to get white. In other words, it doesn't work great, and don't take it camping.
All in all, I am pleased with how this went. I am not done, not by a long shot. I wasn't able to make my light detector (lux) work very easily with the xively account, so I had to settle for the photoresistor. I will repeat this soon with the Lux sensor and will play with the positioning of the glow sticks as well.
Thanks, for all of the suggestions to make this work. If you can see anything else that is interesting please let me know. My goal would be to connect this to kinetics for a general chemistry class.