Why do these spotlights abruptly end rather than fading away?

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We were watching a light show that had a bunch of spotlights the other night (Ocean Cay lighthouse show if anyone is curious). The four beams on the right side of the lighthouse (as seen in the photo) just suddenly ended after some distance as shown in the second photo. What causes this? I would have expected the light to fade gradually to nothing.

Note that it looked exactly like this to the naked eye — the phone did a fantastic job of capturing what I was seeing.

Sorry – I couldn’t figure out how to post these directly to this sub, but it requires a visual depiction to understand – here are the pics:

[https://imgur.com/a/h2iICLC](https://imgur.com/a/h2iICLC)
[https://imgur.com/a/XyLvB6Q](https://imgur.com/a/XyLvB6Q)

In: Physics

3 Answers

Anonymous 0 Comments

That’s not the lights. That’s the edge of a very sparse cloud. The very bright light from the lighthouse makes the cloud visible. When the beam reaches the end of the cloud, it finds clear air and you can’t see the beam any more. When you see a beam that’s not pointed at you, you’re seeing scattering of the beam by something it’s passing through.

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