- #1
ViolentCorpse
- 190
- 1
Hello PF'ers,
Why is it that two light-bulbs produce twice as much brightness as a single light-bulb would? If we restrict our attention to a single point in space where light from the two sources meet, the waves would cancel half of the time and reinforce half of the time, producing on average no greater brightness than a single bulb working alone, unless the two sources produce all waves exactly in phase all the time, which is highly improbable. The brightness would be constantly fluctuating, but I guess our brains are too slow to observe that (not claiming that this is indeed what actually happens).
I know that coherent light is a prerequisite for interference effects and everyday sources of light aren't coherent, but still light behaves like a wave in most ordinary circumstances so there should be some discernible interference on average at least?
Why is it that two light-bulbs produce twice as much brightness as a single light-bulb would? If we restrict our attention to a single point in space where light from the two sources meet, the waves would cancel half of the time and reinforce half of the time, producing on average no greater brightness than a single bulb working alone, unless the two sources produce all waves exactly in phase all the time, which is highly improbable. The brightness would be constantly fluctuating, but I guess our brains are too slow to observe that (not claiming that this is indeed what actually happens).
I know that coherent light is a prerequisite for interference effects and everyday sources of light aren't coherent, but still light behaves like a wave in most ordinary circumstances so there should be some discernible interference on average at least?