Ron, Yes - Maybe the color is due to argon plasma - which is blue color - but still, it should not be stringy. The glow pattern seems to be coming from only the filament, and too linear to be normal plasma, no? And it is a very long filament. In another video he uses that same bulb, and the yellowish light is seen which is more typical. Presumably they are both filled with the same gas.
If the color were indicative of the blackbody radiation of tungsten, the shift from yellow to blue represents about a 5000 degrees increase in temperature, nearly double. Here is a chart that displays the applicable temp -> color variation in a dramatic way: http://en.wikipedia.org/wiki/File:PlanckianLocus.png Since the intensity of light is less than expected with grid AC going through the bulb, but the spectrum is shifted to blue, it seems like it must be some kind of surface near field effect where the argon plasma stays very near the metal as if captured. OK. Eureka! just had a flash of insight. Here is a close-up of a typical tungsten filament, showing the very tight secondary helix that is hard to see without magnification. http://twinkle_toes_engineering.home.comcast.net/~twinkle_toes_engineering/t ungsten_filament.jpg Perhaps argon plasma stays within this helix and gets heated by induction and captured in a linear string? This is kinda like the 'stellarator' of project Sherwood, but that is giving away my age. -----Original Message----- From: Ron Wormus Jones It looks like he ionized the Argon gas in the bulb. Is he using RF modulated with audio frequency sq waves? Still it should get hot. Ron http://www.youtube.com/watch?v=VKzkvoTsixY&feature=related > why is this light emission blue? The implications of a tungsten filament > emitting at a higher frequency than expected is intriguing ...
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