Our office and school fluorescent tube lights are similar but the gas also contains traces of other atoms such as mercury so that the tubes produce ultraviolet (UV) instead of visible light. The glass tubes are coated with a fluorescent material which glows in the UV and this is the bright white light you actually see when the light is switched on.
In both types of light if the voltage drops, or perhaps they are old and some air has leaked into the tube, the light will be unstable and flicker.
This is very annoying if you happen to live opposite a large neon sign 'on the blink'!
You can't see this in the photo but I set up a simple experiment to investigate it which you could try in the school / college lab. I placed a solar cell next to the flicker bulb and then darkened the room. The flickering light produced a varying voltage from the cell which I recorded on a computer data logger (see data above). The regular sharp pulses are due to the 240V AC mains turning the light on and off every half cycle but you can also clearly see the intensity of the light received by the solar cell randomly fluctuating over time. The computer also allowed me to analyse the data in 'spectrum view'. This showed the flicker rate (the way the flashes per second (Hz) vary over time) was fairly random too. To the eye the bulb seems to flicker regularly even though it's random. This is rather like the way a flag flaps in the wind - random motion that looks periodic - a classic chaotic system.
Randomness and chaos are at the heart of many transformations and interactions in chemistry. As a reaction progresses their presence usually becomes averaged out and covered up, but in this simple inert gas flicker bulb we get a glimpse of it.
home | diary | whats on | CSC summary | latest news