You might have a dimmer switch in your home. When you turn the switch one way the lighting will go low, so it is dimmed. Turn it the other way and the light will go very bright. When you go to the cinema you see the lights go dim just before the film starts. How does it work? Inside the light bulb there is a filament and the electric current goes through it. By turning the dimmer switch you reduce the amount of electric current (electrical energy) that can get through the filament. So that's why the bulb dims and there is less light energy.