and apex angle (how the light spreads), and then a bunch of calculus (Φv = 2πIv (1−cos α/2), if you're playing along at home). If you had an LED with the same spread and intensity as an ...

LED bulbs are supposed to last for years -- some even claim up to 25,000 hours of light. So why do so many burn out way ahead of schedule, sometimes within a year? If you’ve ever replaced an ...