Final answer:
The term used for measuring light output in lumens relative to power input in watts is luminous efficacy. It is key in evaluating the efficiency of light bulbs, especially when comparing traditional incandescent bulbs with energy-saving CFL and LED bulbs which offer higher luminous efficacy.
Step-by-step explanation:
The term used for measuring the output of light (lumens) compared to the power input (watts) is known as luminous efficacy. Luminous efficacy is a measure of how well a light source produces visible light, expressed as lumens per watt. It is an important metric for energy-saving light bulbs such as compact fluorescent lamps (CFLs) and light-emitting diode (LED) bulbs, which are designed to provide a higher luminous efficacy than traditional incandescent bulbs.
When comparing bulbs, it's important to look at the lumens to understand the brightness the bulb will provide, rather than just the wattage. For example, a 60-W incandescent light bulb can be replaced with a 6- to 8-W LED bulb that produces the same amount of light, approximately 800 lumens. This demonstrates the efficiency of LED bulbs in delivering the same brightness with significantly lower energy consumption.