Electric torch, coloured X-ray. The torch contains two batteries (black, centre and lower centre) for supplying electrical power to the bulb. This bulb (upper centre) is at the centre of a reflector, a bowl-shaped (parabolic) mirror that reflects light from the bulb and throws it forward, focussing it as a narrow beam of light for better visibility. A torch may have a switch, but many are now turned on and off by twisting the head on a screw-mounted and spring-loaded base to make contact with the batteries and adjust the focus of the beam.