What causes lights to dim?

i dont know maybe your lightbulb is messed up. There could be many possibilities depending on the situation. If a high wattage unit comes on (like an air conditioner), there could be a drain on the system that causes a light to dim. Sometimes during a storm, there could be a problem at the power substation including a power surge or break in the system, that could cause lights dimming. If too many strands of lights in a series are connected, you run the risk of overloading that circuit, which could cause dimmed and blown lights, and potentially dangerous situations.

Consult a Master Electrician for more information.