On February 1 Leigh Palmer wrote:
> I tipped a 300 watt tungsten halogen "torchiere" lamp (cheap at the mall)
> over on its side to illuminate the top .. the instantaneous lamp temperature
> varied. My 1/10,000 second shutter speed reveals clearly the appreciable
> variation in the tungsten filament temperature. Even this incandescent source
> has a small stroboscopic effect, something that was certainly a big surprise
> to me. The effect would be greater for a tungsten halogen lamp than it would
> be for a conventional nitrogen filled bulb because the peak temperature of
> the former is greater, and it cools faster.
Very surprising. The time interval between the peaks of I^2 (at 60 Hz) is
only 1/120 s. And this is sufficient to overcome the "thermal inertia" of
a tungsten fillament. Amazing. How thin must the fillament (a black body
source) be to make this possible?