Lightbulbs continue to glow briefly after power is turned off due to filament heat.
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SUPPORTED
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refutedsupported
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AS REPORTEDno primary record reached; this is what the reporting says
Physics explanations confirm that incandescent lightbulbs maintain a brief residual glow after power is turned off because their filaments take time to cool down from high operating temperatures.
# Why do lightbulbs continue to glow after the light is turned off?
Tags: thermodynamics, thermal-radiation, electromagnetic-radiation, home-experiment
- Score: 18
- Views: 39371
- Answers: 4
- Answered: yes
- Asked by: Whitney
- Asked: 2010-11-17
- Edited: 2010-11-18
- Site: physics
## Question
I've noticed that whenever I turn the lamp off in my room at night, the lightbulb seems to continue to glow for a minute or so after that. It's not bright though; the only way I even notice it is if the room is dark. So why does it keep glowing?
## Answers
### Answer by Chad Orzel (score: 31 [ACCEPTED])
If it's an incandescent bulb, it's because the whole operating principle of the bulb is based on getting the filament really hot, hot enough to glow. When you cut off the current, it stops heating the filament, so it cools down fairly rapidly, but there may be enough residual heat for a faint glow lasting a little while afterwards.
If it's a CFL bulb or an ordinary fluorescent bulb, the "white" color we see is produced by a fluorescent coating on the glass of the bulb, which converts some of the invisible ultraviolet light produced by the excited gas atoms into visible light. When y
# Why does light fade from a room?
Tags: electromagnetism, visible-light, radiation
- Score: 1
- Views: 1571
- Answers: 2
- Answered: yes
- Asked by: QCD_IS_GOOD (7277 rep)
- Asked: 2014-10-25
- Site: physics
## Question
So basically in my toilet I have this really bright ceiling light, but when I turn it off it doesn't just instantly plunge me into darkness, but rather sort of fades out over a few seconds. It looks just like a bulb light to me, but it's pretty high up so I can't check it.
Conjecture: the bulb works by heating a wire, which at high temperatures gives off light, and when I flick off the switch it doesn't just instantly cool down, it takes a while, and with residual heat gives off less and less light with each passing second.
But if this is the case, I'm still a tad confused. I thought that for radiation like this the wavelength should vary with the heat produced? If so, when it dims, shouldn't the light change color to a more reddish and pinkish (less energetic) wavelengths? Instead what I observe is that it just keeps the same warm yellow glow, just getting less and less bright as time goes on. Or are my eyes too bad at detecting such a small change?
Tried s
Everything we examined (2) — 1 independent source
This check searched the claim as stated. It did not run a separate search for evidence against it.