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To: lentulusgracchus
Halogen bulbs on AC current and fluorescents tend to flicker invisibly at 50Hz or 60Hz, which causes eyestrain as the iris tries to follow the flickers and adjust.

Obviously you have NO idea how flourescent bulbs operate. Go google and read the description of the operation of the ballast. You will see that they DO NOT have a 60hz component, it is more like 40Khz!

69 posted on 01/22/2011 12:37:39 PM PST by SeeSac
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To: SeeSac

If you have better knowledge, please post up. Link, please.


72 posted on 01/22/2011 7:00:43 PM PST by lentulusgracchus (Concealed carry is a pro-life position.)
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To: SeeSac
Obviously you have NO idea how flourescent bulbs operate.

Oh, and here's my put-up on this business of flickering fluorescents:
http://www.essex.ac.uk/psychology/overlays/1988-76.pdf

[From the Introduction]

Introduction

An intermittent light no longer appears to flicker when the frequency exceeds some limit commonly referred to as a flicker 'fusion' threshold. When the light is bright and diffuse and stimulates a large retinal area this threshold can be as high as 90 Hz but is rarely higher(l). The 'fusion' threshold cannot, however, be taken as a limit above which intermittent light has the same effect as continuous light. First, Greenhouse and colleagues(2) have recorded human electroretinogram responses to intermittent light at frequencies higher than 100 Hz. Second, Brindley(3) demonstrated psychophysically that the nervous system resolves intermittent light at frequencies at least as high as 125 Hz. He stimulated the retina electrically so as to produce the appearance of flashes of light (phosphenes). When he increased the frequency of electrical stimulation sufficiently the phosphenes appeared continuous. Brindley combined electrical stimulation and stimulation from flickering light simultaneously, at frequencies at which both forms of stimulation appeared continuous when presented on their own. When the frequencies of the combined electrical and visual stimulation were slightly different observers reported seeing the beat between the two. The beat was perceptible when the visual stimulation had a frequency as high as 125 Hz indicating that, at some level, the visual system was resolving the stimulation at this frequency.

Fluorescent lamps operating on an AC supply emit light that pulsates in brightness(4). Twice with each cycle of the electricity supply (e.g. at 100 Hz) the light output varies between a maximum and about 60% of that maximum, depending on the decay rates (persistence) of the phosphors and the range of wavelengths measured. The light output also varies slightly at half this frequency (i.e. at the frequency of the AC supply) partly because the dark spaces in front of the cathode alternate between the ends of the tube, and partly because the electrodes may burn unevenly, and as the tube ages an asymmetrical discharge can result.

--Paper by Wilkins, Nimmo-Smith, Slater, and Bedocs, rev. version 1989. (full cite at link)

There you are. As I was saying. Without a special ballast, US fluorescents would (did) flicker at 120 Hz, the house-power cycle rate X 2 (not 60Hz, my bad, good ding), but then at 60Hz later on, as they age (oops). If they were on 410Hz AC service, like some military applications, there'd be less of an eyestrain problem, as I've pointed out -- but they'd still flicker. More links available.

73 posted on 01/22/2011 8:06:39 PM PST by lentulusgracchus (Concealed carry is a pro-life position.)
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