A challenge (1 Viewer)

mikhail

Senior Member
Jan 24, 2003
9,575
#1
If you look at the intensity of sunlight on a spectrum analyser, it shows a big DC component. If you look at the same thing for an artificial light, it shows a big AC component at 100Hz (120Hz in the US and, bizarrely, half of Japan). Can anyone tell me why this is, given that the frequency of the electrical supply is 50Hz (60Hz)?
 
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mikhail

mikhail

Senior Member
Jan 24, 2003
9,575
#3
Finally found the answer to this one:

The maximum amplitude of the voltage, and thus a maximum brightness, occurs twice per cycle because an electric bulb is excited when the voltage increases, regardless of the polarity of the voltage.
 

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