 
 <prompt> Wetin be di ratio wey dem dey use to determine how effective something be? Based on di question wey dey above, write one context wey go contain di answer. E fit be 1 - 20 sentences. Context: <response>: ```One important property of light fixtures na di luminous efficacy or wall-plug efficiency, meaning di amount of usable light wey dey come out from di fixture per energy wey dem use, usually measured in lumen per watt. A fixture wey dey use replaceable light sources fit get efficiency wey dem go quote as di percentage of light wey dey pass from di "bulb" go di surroundings. Di more transparent di lighting fixture be, di higher di efficacy. If dem shade di light, e fit reduce efficacy but fit increase di directionality and di visual comfort probability.``` 