Alan, iwire
Nice theory, er...except that a bulb is switching off and on 60 times a second anyway, in harmony with any arc.
The keyword here is
thermal inertia. A filament takes a bit longer than 1/120s to cool down significantly. That's why with bulbs you usually do not have the stroboscopic effect (that's the one that makes some car wheels on TV stand still or go backwards).
A dimmer prolongs lamp life by operating the filament at lower temperatures (= less light, color is yellow/orange). The filament does not care about the horrible waveform feeding it. I've used small bulbs as load devices for all kinds of waveforms, even true power spikes, they don't care as long as you don't exceed the rated power dissipation (the integral of voltage times current over time). Not to say that these bulbs didn't suffer from being "switched" on and off by low-periodicity spikes...
