Accidental in the Same Measure Question

[Newbie]

I've noticed that the same accidental is repeated in a measure and I'm curious about the reasoning behind it. Can anyone shed some light on this?

[GearNerd]

This is a common thing people don’t know: An accidental on a note applies to that note AT THAT PITCH, IN THAT OCTAVE only. The first F# applies only to any F notes in the first space (in this measure of course). The F on the top line needs its own accidental because it’s a different F than the previous one that was sharped.

[MetalPlayer]

It’s because it’s in a different register. Accidentals apply only to that specific pitch in that particular octave.