ABSTRACT
In this chapter, the authors determine the color of water, or more accurately stated, the absorption of material dissolved in water. They investigate the absorption of light of different colors by turning a three-color light-emitting diode (LED) on and off, and observe the resulting modulation of the signal recorded by a phototransistor. If red light is absorbed, the resulting modulation depth of red is reduced, likewise for the other colors. If red light is absorbed, the resulting modulation depth of red is reduced, likewise for the other colors. By comparing the situation with LED on versus off, the system removes some of the influence of ambient background light, at least to some extent. The authors construct the setup to measure the color-dependent absorption and the reflection from a surface, using an Arduino UNO, and an RGB-LED, which houses a red, a green, and a blue LED in the same housing with a single connector for a common cathode or anode.
