skykooler&#x27;s point is that the Sun is not a point source. I think you may be mentally modeling it as a point source. A point source would make it just a matter of length, but when it&#x27;s not a point source you can&#x27;t help but get overlap between two &quot;points&quot; that are close enough together, because they both will be lit up at the same time, no matter how long the tube may be.