Laser trails

[bascule]

Why does a moving laser leave a perceived trail in your vision? Is this due to a chemical reaction in the retina? A secondary effect in the brain?

[AngryTurtle]

I don't believe i'm following exactly what you are saying, but you can't see a laser unless its bouncing off of something (dust particles) in the air and travels at the speed of light so you might have better eyes than my own but I can't really watch things as they move at the speed of light

[John Cuthber]

Are you talking about a persistence of vision effect?

[Mr Skeptic]

Your eye produces photosensitive chemicals, to detect light. These chemicals are constantly destroyed by light and replaced. An excessively bright light will use them up quickly, leaving a temporary shortage of them, so that normal light viewed as less bright in the affected cells, for a while. This will result in a slight negative image that lasts a while.

 

Is that what you are talking about?

[bascule]

  Mr Skeptic said:

Your eye produces photosensitive chemicals, to detect light. These chemicals are constantly destroyed by light and replaced. An excessively bright light will use them up quickly, leaving a temporary shortage of them, so that normal light viewed as less bright in the affected cells, for a while. This will result in a slight negative image that lasts a while.

 

Is that what you are talking about?

 

That happens as well.

 

I'm talking about if you point a laser pointer at a wall and make little loops with it. The laser appears to leave a trail in your vision. Part of that trail does consist of a negative image, yes, but another part appears just as bright as the laser itself.

[Sisyphus]

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

 

I don't know if that's the whole explanation, but it's definitely part of it.