What Causes the Strange Effect on this Exit Sign?

  • Thread starter Thread starter fawk3s
  • Start date Start date
  • Tags Tags
    Interesting Sign
Click For Summary

Discussion Overview

The discussion centers around a peculiar visual effect observed on an exit sign in a school, which resembles light patterns typically seen in water. Participants explore potential causes for this phenomenon, considering various types of light bulbs and their behaviors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a visual effect on an exit sign that resembles light patterns seen in water, suggesting it might be related to the fluorescent bulb behind the sign.
  • Another participant notes that light bulbs and tubes can flicker, which might produce similar effects, and mentions that specific bulbs are designed to create such patterns.
  • Some participants clarify that fluorescent tubes do not contain filaments, which challenges the initial hypothesis about the bulb's construction.
  • There is a suggestion that the observed effect could be due to flickering, with one participant sharing an experience where vibrations caused flickering in an old bulb.
  • Another participant argues that the effect appears more ordered than typical flickering, questioning how vibrations could produce such slow waves.
  • One participant explains that fluorescent lights can flicker at twice the mains frequency, which may not be visible under normal conditions, but can lead to observable patterns in older bulbs.
  • There are humorous comments about the design of the exit sign itself, with participants discussing the imagery depicted on it.

Areas of Agreement / Disagreement

Participants express differing views on the cause of the observed effect, with some attributing it to flickering and others questioning this explanation. The discussion remains unresolved regarding the exact mechanism behind the visual phenomenon.

Contextual Notes

Participants mention various factors that could influence the flickering effect, including the age of the bulb and the characteristics of the ballast circuit, but do not reach a consensus on the primary cause.

fawk3s
Messages
341
Reaction score
1
So today I noticed something pretty weird on an exit sign above a door in my school, looking somewhat like this:
http://www.examiner.com/images/blog/wysiwyg/image/exit_sign.jpg

The effect is pretty difficult to describe by words, since I didnt expect to see anything like that on it. But it looked somewhat like the effect you would get in a dim pool room in the ceiling when the light in the pool would be on - a nice play of light by the water waves.
And this effect was in the sign, which presumably has a fluorescent light behind it. Ofcourse the effect is only on the sign and there is no water whatsoever nearby, so please let's rule this out. What could cause this effect?

I have no good guess besides maybe that the fluorescent bulb might have a filament or something inside it, which makes contacts with the glass shield and acts somewhat like a plasma lamp would? I know, crazy theory, plus I haven't heard of any of these kinds of bulbs, but its the best one I've got so far.

Any ideas?

Thanks in advance,
fawk3s
 
Science news on Phys.org
Light bulbs and tubes flicker, I've had some that do it and produce the effect you're talking about to varying degrees.

You can actually buy bulbs specifically designed to reproduce it.

Flourescent tubes don't have filaments.
 
jarednjames said:
Light bulbs and tubes flicker, I've had some that do it and produce the effect you're talking about to varying degrees.

You can actually buy bulbs specifically designed to reproduce it.

Flourescent tubes don't have filaments.

I know they dont, but I figured maybe it was a plasmalamp-like bulb in there, which wouldn't make much sense anyways so never mind.
But what is the effect actually caused by? It can't be just flickering.

Thanks in advance,
fawk3s
 
fawk3s said:
But what is the effect actually caused by? It can't be just flickering.

Why not?

I have an old ish bulb where the filament is particularly secure and any vibration causes a flickering effect.
 
But it doesn't look anything like flickering nor vibration, these are slowish, looking somewhat ordered waves. I can't really imagine how a vibration could cause that, especially as they are slow-looking waves.
 
Its prob caused by the flicker of the bulb, all bulbs do this as ac power has an off phase in its wave, added to the after image caused by your eyes delayed reaction to the flicker
 
Yeah, fluorescent lights can do that. They flicker at twice the mains frequency, so it's not normally visible. But old ones can start flickering more or cause the patterns you saw. I think it's because you get some resonance with the ballast circuit that's not supposed to be there, normally. Same thing can cause them to make noise.Why is the guy on the sign wearing a cape?
 
This exit sign is hilarious. That guy's bolting for the door. It should be the bathroom sign instead.
 

Similar threads

High School Can someone explain this projection distortion effect
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad What Determines Whether Radiation Passes Through Materials?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad A busy and interesting night sky in Mackinaw City
  • · Replies 1 ·
Replies
1
Views
2K
High School I need a very unusual UV filter (no, not what you're thinking)
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Edison effect for Incandescent Bulb?
  • · Replies 3 ·
Replies
3
Views
5K
Undergrad What caused the strobe effect on the raindrops during the thunderstorm?
  • · Replies 14 ·
Replies
14
Views
2K
What Unique Microscopy Samples Can Engage Kids in STEM Learning?
  • · Replies 4 ·
Replies
4
Views
3K
Flickering neon bulb, what causes the flicker?
  • · Replies 17 ·
Replies
17
Views
33K
Graduate What is the Relationship Between Cause and Effect in Spacetime Geometry?
  • · Replies 16 ·
Replies
16
Views
3K
What Are Realistic Mid-Journey Disasters in Interstellar Travel?
  • · Replies 118 ·
4
Replies
118
Views
13K