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I have a question about beams...

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Hello all,

As the title says I have a question about the beams of the lasers. I don't know that much about physics, but why does the beam of lasers when seen from distance seem to stop at some point but the light itself keeps on going ?

Here are some examples:


You see the one from the Eiffel tower how the beam "stops" quarter way...Why doesn't it continue further ? Or when you point it at the sky, it also "stops" at some point.

Thank you.
 

Eudaimonium

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Imagine you're holding an infinitely long stick in your hand. Wouldn't it also appear to "stop" at some point in the sky?

Besides, in laser beams, you've got divergence, and loss of power through atmosphere as well, dictating it's visibility. Air isn't completely transparent. If it were, we wouldn't see any beams at all.
 
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Imagine you're holding an infinitely long stick in your hand. Wouldn't it also appear to "stop" at some point in the sky?

Besides, in laser beams, you've got divergence, and loss of power through atmosphere as well, dictating it's visibility. Air isn't completely transparent. If it were, we wouldn't see any beams at all.
I get it now, it's because of divergence. At some point the photons aren't so concentrated because the beam is getting wider.
 

Eudaimonium

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Well that's only part. Like I said, imagine you're holding an infinitely long lightsaber. It'll still appear to be poking one place in the sky instead of...

I dunno, how do you even imagine an alternative? :D
 

Blord

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It is the same effect as you looking at railways. They "stop" somewhere at the horizon.
Imagine you shine the laser in the air, the dot is always on the horizon.

 
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