Instantaneous show of light why?

[wayneinsane]

Does anyone know a clear and absolute explanation of how is it that when you flick the light switch on there is an instantaneous show of light?

 

[Delphi51]

It isn't instantaneous, just too fast for you to notice (unless using curly fluorescent bulbs).
The electrical energy travels through the wiring at about half the speed of light, so that doesn't take long. The biggest delay is the time needed to heat the filament in the bulb.