what do we mean when we say a point light source is [tex]5.0 mW[/tex]
That is an energy - so not very useful, unless it means 5.0mJ/s ie 5milliWatts.
In astronomy it could be a typo for mJy = milli Jansky bit this isn't commonly used for visible light
sorry that was watt.
It's not energy, it's power. It means the light source is giving out energy at the rate of 5 J/s.
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