Timeline for Can one see flickering of a light bulb at 50 Hz?
Current License: CC BY-SA 4.0
23 events
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| Aug 21, 2018 at 17:40 | comment | added | vsz | It might be that it's a very cheap LED light, and uses only a half wave rectifier instead of a full bridge. This means every other wave is turned off, and the lamp spends at least half its time completely switched off. This also makes it flicker at half the frequency it would with a full bridge rectifier. | |
| Aug 21, 2018 at 11:29 | comment | added | SF. | You can definitely see if a lightsource is continuous or flickering, by observing rapid motion. Wave a bright (like, white) object lit by that source in front of your face. With flickering light you'll notice multiple separate images. | |
| Aug 21, 2018 at 10:08 | comment | added | fdomn-m | Doesn't appear to be mentioned in the answers: your peripheral vision is much better at noticing movement that your focused/central vision. This is why you noticed it "out of the corner of your eye" but when you looked at it directly you couldn't see the change. Old CRTs have been mentioned and it was quite obvious if you put two side-by-side (and 1metre/3feet apart) and looked at one: the other would appear to flicker but not the one you were looking at. | |
| Aug 21, 2018 at 4:02 | answer | added | Artelius | timeline score: 3 | |
| Aug 20, 2018 at 20:14 | comment | added | David | I seem to recall reading multiple times statements from autistic persons who claimed they could see fluorescent light bulbs flicker. (I have a child on the spectrum. This would have been when he was preschool age, and he is now 18, so it was some time ago.) IIRC the thinking was, it's not so much that very few people can see this but that most of us have learned to filter/ignore it. We live in the US so this would have been 60 Hz. | |
| Aug 20, 2018 at 16:00 | comment | added | user21820 | @jamesqf: Yes indeed. Especially those that deliberately pulse on and off, but what I found interesting was that some fluorescent tubes that give 'warm light' are not monochromatic, and I discovered it exactly by flicking my line of sight across them, the first time accidentally. | |
| Aug 20, 2018 at 15:53 | comment | added | jamesqf | @user21820: This is quite noticable (at least for me) with LED car tail lights, especially at night when I'm a bit tired. Sometimes traffic signals & advertising signs, too. Part of it, I think, is that they often use pulse width modulation to control the light intensity... Also note that a bad or failing LED or CFL bulb can flicker. | |
| Aug 20, 2018 at 12:13 | comment | added | rcgldr | @Timo - possibly a CFL (compact fluorescent light) bulb (usually a coiled tube). CFL bulbs could change intensity nearly instantly, but there's usually some capacitance in the circuitry which would reduce flicker. | |
| Aug 20, 2018 at 10:42 | comment | added | Timo | @rcgldr It was some sort of energy saving bulb (Not sure which type, but not LED). Not a incandescent bulb. | |
| Aug 20, 2018 at 9:48 | comment | added | user21820 | It is actually not hard to detect on-off flicker at 50 Hz with your eyes even in well-lit surroundings. Simply flick your line of sight across the flickering light source, and you will see a regularly spaced sequence of images for a split-second in your visual field. There are even some electrical lights that oscillate between different wavelengths, and such a technique will allow you to see it. Also, even if you do not do this on purpose, you may notice the effects when you shift your gaze or during the natural saccades of your eyes. But incandescent bulbs hardly flicker, as @rcgldr said. | |
| Aug 20, 2018 at 6:04 | answer | added | StessenJ | timeline score: 8 | |
| Aug 20, 2018 at 2:41 | comment | added | rcgldr | You didn't mention if this was an incandescent bulb. If so, it seems the filament's brightness wouldn't change that much during a 50 hz cycle, but it's possible. | |
| Aug 20, 2018 at 0:01 | history | tweeted | twitter.com/StackBiology/status/1031330368480313349 | ||
| Aug 19, 2018 at 21:38 | comment | added | Timo | @Criggie No intoxication whatsoever - funcact: my friends asked me the same question when I told them :D | |
| Aug 19, 2018 at 21:16 | comment | added | Criggie | Sub-question - had you been drinking alcohol? I'd guess that would have slowed down your reactions/perceptions though. | |
| Aug 19, 2018 at 19:24 | history | edited | AliceD♦ |
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| Aug 19, 2018 at 19:05 | history | edited | AliceD♦ | CC BY-SA 4.0 |
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| Aug 19, 2018 at 18:45 | history | edited | AliceD♦ | CC BY-SA 4.0 |
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| Aug 19, 2018 at 18:39 | history | edited | AliceD♦ | CC BY-SA 4.0 |
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| Aug 19, 2018 at 18:38 | vote | accept | Timo | ||
| Aug 19, 2018 at 18:36 | answer | added | AliceD♦ | timeline score: 33 | |
| Aug 19, 2018 at 17:40 | review | First posts | |||
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| Aug 19, 2018 at 17:32 | history | asked | Timo | CC BY-SA 4.0 |