Why Do Bright Lights Have Rays

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Discussion Overview

The discussion revolves around the phenomenon of bright lights appearing to emit rays, as observed in sources like the sun or car headlights. Participants explore the visual effects produced by these light sources, considering both human perception and photographic representation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the nature of bright lights emitting distinct rays rather than a uniform glow, seeking an explanation for this visual effect.
  • Another participant suggests that the rays may be related to diffraction spikes, indicating that atmospheric and ocular artifacts could enhance these effects, particularly with brighter sources.
  • A different participant notes that while a photograph captures this effect, it may not be directly comparable to human vision, proposing that imperfections in a camera's aperture could contribute to the observed rays.
  • One participant argues that the eye and camera function similarly, both having lenses and diaphragms, and suggests that the geometric nature of rays in cameras is influenced by diaphragm shape, although they believe the underlying mechanisms are not substantially different.

Areas of Agreement / Disagreement

Participants express differing views on the causes of the ray-like appearance of bright lights, with no consensus reached on the primary mechanism or whether the effects in human vision and photography are comparable.

Contextual Notes

Some assumptions about the mechanisms of light perception and the role of diffraction and aperture imperfections remain unresolved, and the discussion does not clarify the extent to which these factors contribute to the observed phenomena.

peter.ell
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I'm not sure if anyone knows, or if this really is a physics question, but I was wondering why bright lights always seem to have rays emanating from them.

What I mean by this is that bright lights, such as the sun or a car's headlight, always seem to radiate light in visibly distinct bright lines encircling the light source. This is apparent to our eyes as well as cameras, but what actually causes the light to radiate in spatially separated lines of light rather than circularly and uniformly?

Take a look at this for an example of what I mean: http://www.homesolarinfo.com/image-files/sun-clouds-sky-picture2.jpg

Thank you!
 
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Hrmm, that looks a bit like a Diffraction Spike. See here for more info.

http://en.wikipedia.org/wiki/Diffraction_spike

I believe they are most likely due to similar effects. The atmosphere and your eye produces "artifacts" or whatnot of the light that are more pronounced the brighter the source is.
 
That is a photograph though. Not quite the same as an eye.

Actually looking at it it looks a bit like a retina, could they be produced by minor imperfections in the aperture of the camera?
 
AtomicJoe said:
That is a photograph though. Not quite the same as an eye.

Actually looking at it it looks a bit like a retina, could they be produced by minor imperfections in the aperture of the camera?

I believe your eye produces diffraction effects as well. I don't know any details though.
 
Eye and camera are not that different. You have a lens, a diaphragm, and a light sensitive surface. There is a difference in a diaphragm shape - that makes "rays" in the camera much more geometric, but other than that there is no reason for substantially different mechanism in both cases.

Or at least that's how I see it.
 

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