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A surprising physical observation

I wandered my dark house with an ultraviolet LED in one hand, illuminating stuff. I saw mostly expected results, i.e. fluorescence from the optical brighteners that manufacturers impregnate in paper and textile products to make them appear whiter/brighter… cotton towels, printer paper, and the sticky labels on various boxes in my office all light up with a dim blue glow when hit with the UV-LED. Somewhat unexpectedly though, my glass of Athena ouzo exhibited a nice violet fluorescent emission. I blame that on its high concentration of anethole, the essential oil of anise, an aromatic molecule with a benzene nucleus. Count ouzo with tonic water, which also fluoresces under blacklight. None of this surprised me enough to write this post though.

What surprised me was this: the UV-LED works as a remote control for neon lamps. I have several power strips in my office. You’re probably familiar with the kind that has a neon bulb illuminating the power switch. That’s the flickering orange glow inside the switch - a small glass envelope containing neon gas and two electrodes. Anyway, I’m getting ahead of myself. Here’s what happens. Standing in the dark office, nothing is emitting light. I click on the UV-LED, and immediately, the neon bulbs in my two power strips respond by illuminating with their typical glow. I’ve always wondered what governs these things. If you’ve ever watched them sit there and flicker, you might wonder if its due to variations in AC line voltage, or some other characteristic of the gear drawing power from the power strip. Maybe thats true - but right now I’m able to control the neon lamp from across the room with my UV-LED, with near 100% accuracy. It’s a surprisingly sensitive phenomenon. From ten feet away, I’m pointing the LED at the power strip. For every flash I make with the LED, the neon lamp in the power strip responds instantly by flickering its orange glow.

Hypothesis as to why this works? A neon lamp only glows when the voltage across its terminals exceeds a threshold value. I suppose that somehow the power strip lamps are biased to a point near emission but not quite. The ultraviolet photons from the LED hit the neon atoms, and provide the extra tiny bit of energy to pop an electron up into an excited state. From that point, the orange glow takes place automatically.

I was a “C” student in college physics though.

Can you think of alternative explainations? Or perhaps something clever that can be done with this phenomenon? I’m going to sleep on it.