Eli5 Why is it that, in some rooms, when you turn on the light there’s a delay, but when you switch it off, it turns off instantly?
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When you see a brief delay in turning on a light, it’s because either the lamp has some kind of ballast or driving system that has to charge up, or because you’re using some kind of “smart” device to control the lights, and it takes a moment to detect the input and change the state of the lamps.
Incandescent bulbs will turn on instantly when power is applied. However, fluorescent and LED bulbs may take a moment to light up because they have control circuitry in them that must power up before power is delivered to the actual element that provides light, or in the case of fluorescent bulbs, the gas in the bulb may take a moment to be fully ionized and begin emitting light.
They turn off instantly because while it may take a moment for the control circuitry and/or the gas in a CFL lamp to turn on, removing the power turns everything off instantly.
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