The dimming is generally done on the AC side before it even reaches the bulb. So it would be dimmed by either resistive (unlikely) or by cutting the AC waveform

The dimming is generally done on the AC side before it even reaches the bulb. So it would be dimmed by either resistive (unlikely) or by cutting the AC waveform by timing the zero crossing point. For more information, and a look at the waveform that is produced see this awesome page: http://www.epanorama.net/documents/lights/lightdimmer.html http://www.epanorama.net/documents/lights/lightdimmer.html