pHantastic Fluorescence

In this Activity, students easily extract a fluorescent substance from shavings of a wood called narra. The fluorescence is dramatically pH dependent and can be turned on and off repeatedly using commonly available acid and base solutions. The striking blue fluorescence is the result of absorbing light from a black light and in response emitting longer wavelength visible light. Sunlight and standard fluorescent room lighting can also cause the solution to emit the blue fluorescence. A yellow filter will block the ultraviolet (and violet) light but not the fluorescent emission.