Which device is used to control the intensity of light in a spotlight?

The device used to control the intensity of light in a spotlight is a dimmer. Dimmers adjust the amount of electrical power sent to the light source, allowing the operator to modify the brightness of the light output. This is essential in creating various lighting effects during performances, as it enables the fine-tuning of the illumination to suit the mood and atmosphere of the scene.

In contrast, the shutter is primarily used to block light or create shapes, rather than control its intensity. The reflector serves to direct and focus the emitted light, enhancing its efficiency, but it does not adjust brightness. The lens also plays a crucial role in focusing or softening the light beam, but like the reflector, it does not control intensity. Therefore, the dimmer is the key device in managing the brightness of spotlighting in theatre settings.