BRUSH UP ON LIGHTING

AMPS Amps are used, along with volts, to calculate watts. Watts represent how much power a light source uses

BEAM ANGLE This measures the spread of a light source — the wider the beam angle, the better the spread of light

CAP The part of the light bulb that connects it to its fitting (usually bayonet or screw)

DELIVERED LIGHT This is the amount of light delivered by a luminaire — measured in ‘lux’ which indicates the brightness of light over a given area

DIMMER SWITCH These allow you to adjust the brightness of a bulb or bulbs. LEDS are also dimmable but must be used with Ledspecific dimmer switches

LED This stands for Light Emitting Diode. LEDS are highly efficient and last three times longer than Compact Fluorescent Lamps (CFL) — and 30 times longer than incandescent bulbs

LUMENS These are units of luminous ‘flux’ — a measurement of the intensity of a light source. A lumen rating (lm) gives the best indication of its brightness

LUMINOUS EFFICACY A term that describes the efficiency of a light source. It compares light output (lumens) to the power a light source uses (watts). This results in a lumens per watt rating (lm/w) PENDANT A light that hangs from the ceiling on a cable

REFLECTOR LAMP A bulb with a silvered inside layer. These produce a soft beam TRANSFORMER These can be used to change the voltage of an electricity supply. Different bulbs need different voltage levels and transformers can be used to lower voltage

TWO-WAY SWITCH These allow you to operate the same light fitting from two different switches in different locations — useful at the top and bottom of staircases or either end of corridors