Light bulb in the room

[warpie]

So, a bit "irrelevant" question but I have a weird behaviour in my room.

I switched off the light switch and the light bulb blinks (lights up for less than a second)  in a frequency of approx.  every 3-4 seconds. 

Any idea?

EDIT: I should have do my research before posting…  Apparently that's not very uncommon with CFL bulbs.
Now, what causes this (the cfl itself or bad/wrong wiring)  and whether is dangerous or not is something I need to figure out.

 

[JohnRoberts]

I have CFL lamps that glow for a while after being turned off... They are fluorescent lamps so may be triggered by noise or low voltage until fully discharged.

Imagine if your light switch and wiring is reversed polarity, so the switch opens the neutral side (0v return), instead of the hot line side. The light bulb when switched off it is still swinging at 120VAC, just with no low impedance return path to neutral. Any capacitance to ground on the floating low side of the lamp wiring could provide a small current/voltage path to the switched off lamp. Perhaps enough for few flashes until the charge inside the lamp is fully depleted. 

Just my speculation...

JR

 

[warpie]

Hey John, yeah reversed polarity might be the case. The house is quite old so everything's possible.
I'll replace the bulb and see. I've never had this problem before so it might well be the bulb that's faulty.

 

[gyraf]

..just remember to turn off your transmitter, switch off all your tesla coils, and close the hatch to the radiation chamber, then most lights will turn off when you flip the switch..

Jakob E.