Light Spectrum:
Mermaids trainer, "Now I'm going to state the obvious here but work with me because I do have a point. Now we've got two light bulbs here and one is on and one is off, do we agree?"
Now, I am not an expert on electricity by any stretch of the imagination, but I know if I go into a dark room, I look for the switch and I will flick the switch and the lights will come on. If I flick it again the lights will go off. I know that much, yeah? So we've got boy/girl, on/off, yeah? Who can tell me what this is?
Audience: a dimmer switch
Mermaids trainer: It's a dimmer switch, and how does a dimmer switch work? I don't mean like transformers and circuits, just very basically, how does a dimmer switch work?
Answer: You turn it and the more you turn it up the brighter it is.
Mermaids trainer Exactly. So it'll start at off, and it will get gradually brighter and brighter and brighter and brighter until the light is completely on, because light is on a ... ?
Answer: Spectrum.
Mermaids trainer: Spectrum, absolutely."
A dimmer switch is used to vary the brightness of compatible dimmable bulbs, allowing a desired level of illumination to be achieved often with the purpose of creating mood lighting. Operated with a rotary adjuster, a dimmer light switch works by reducing power to the lighting source which can avoid harsh glares and beams. This can also help to prolong the life of the bulbs they are operating, which are run at lower power when the dimmer is set at a lesser ambience.
Apologies but this was bugging me: Physics GCSE memories!