Comments on: Pretty traces of light! http://blog.sciencegeekgirl.com/2009/02/01/pretty-traces-of-light/ explorations and inspirations... in how we learn science Mon, 06 Feb 2012 23:52:22 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Stephanie Chasteen http://blog.sciencegeekgirl.com/2009/02/01/pretty-traces-of-light/comment-page-1/#comment-4026 Stephanie Chasteen Mon, 07 Nov 2011 16:23:25 +0000 http://sciencegeekgirl.com/?p=220#comment-4026 Wow, how interesting, Ave. I'm glad that you found out what the issue was. Just FYI, "positive afterimages" aren't in the opposite color from what the original light source is -- above, you describe that you were surprised that it wasn't in the opposite color. That would be a "negative afterimage." Look them up on wikipedia. Your issue obviously wasn't either one, but just so you know, you *can* see a bright image in the same color, caused by the light sensitive cells continuing to fire after you look away from the object. Vision is really weird. As for learning resources -- probably your local community college would be the best. There is also a nice online resource (which costs) called ALEKS, might be worth looking into. Best, Stephanie Wow, how interesting, Ave. I’m glad that you found out what the issue was.

Just FYI, “positive afterimages” aren’t in the opposite color from what the original light source is — above, you describe that you were surprised that it wasn’t in the opposite color. That would be a “negative afterimage.” Look them up on wikipedia. Your issue obviously wasn’t either one, but just so you know, you *can* see a bright image in the same color, caused by the light sensitive cells continuing to fire after you look away from the object. Vision is really weird.

As for learning resources — probably your local community college would be the best. There is also a nice online resource (which costs) called ALEKS, might be worth looking into.

Best,
Stephanie

]]> By: Ave http://blog.sciencegeekgirl.com/2009/02/01/pretty-traces-of-light/comment-page-1/#comment-4022 Ave Fri, 04 Nov 2011 15:35:00 +0000 http://sciencegeekgirl.com/?p=220#comment-4022 Thank you Stephanie! I have had a few other experiences with light and did see an ophthalmologist. He diagnosed a normal aging condition where the gel of the eyeball pulls away somewhat from the back of the eye, causing light images to be repeated. What seemed odd to me was that the repeated image was colored, and not in the 'negative effect' way that a person can cause themselves by looking at a bright image, and having it repeat in the opposite color when looking away. A particular incident was a white chandelier in a fully daytime lit conference room, repeating back to me in fluorescent pink. This occurred in Jan. 2011. The LED rear car light event happened just prior to me blogging you. On another topic - would you know of resources for a 50 year old to learn algebra and physics in an environment that would have plenty of dialogue and personal coaching? I am so interested in a variety of topics that keep pulling me in that direction - but I had trouble in high school and never success. Thank you :) Ave Thank you Stephanie! I have had a few other experiences with light and did see an ophthalmologist. He diagnosed a normal aging condition where the gel of the eyeball pulls away somewhat from the back of the eye, causing light images to be repeated. What seemed odd to me was that the repeated image was colored, and not in the ‘negative effect’ way that a person can cause themselves by looking at a bright image, and having it repeat in the opposite color when looking away. A particular incident was a white chandelier in a fully daytime lit conference room, repeating back to me in fluorescent pink. This occurred in Jan. 2011. The LED rear car light event happened just prior to me blogging you.
On another topic – would you know of resources for a 50 year old to learn algebra and physics in an environment that would have plenty of dialogue and personal coaching? I am so interested in a variety of topics that keep pulling me in that direction – but I had trouble in high school and never success.
Thank you :)
Ave

]]> By: Stephanie Chasteen http://blog.sciencegeekgirl.com/2009/02/01/pretty-traces-of-light/comment-page-1/#comment-4006 Stephanie Chasteen Wed, 19 Oct 2011 16:04:35 +0000 http://sciencegeekgirl.com/?p=220#comment-4006 I don't think you need to get yourself to the doctor -- it just sounds like what's called a "positive afterimage" of the LED light. The LED is either blinking on and off rapidly, resulting in a repeating trace image of the light, or the eye is somehow not seeing a continuous after-image streak but rather a series of discrete after images. This after-image is seen as a streak since you're moving your eye from that vehicle to the point in front of your own vehicle. The swoop shape is probably due to the way that you move your eyes (sounds like you move them down then back up, probably unconsciously) as you move your eye away from the original source. I believe the changing size of the image might be because you are moving from looking at something nearby (the taillight) to something far away (the road in front of you), and so your brain perceives the after-images in front of the road to be smaller in comparison to the other images in front of you. I know that's a confusing explanation in that last sentence -- I can write more if you want -- the basic idea is that the brain perceives size to be relative to the distance of an object. The same size object a mile away, your brain knows to be larger in real life (an elephant) than the same size object right near by (a mouse). Hope that helps! I don’t think you need to get yourself to the doctor — it just sounds like what’s called a “positive afterimage” of the LED light. The LED is either blinking on and off rapidly, resulting in a repeating trace image of the light, or the eye is somehow not seeing a continuous after-image streak but rather a series of discrete after images. This after-image is seen as a streak since you’re moving your eye from that vehicle to the point in front of your own vehicle. The swoop shape is probably due to the way that you move your eyes (sounds like you move them down then back up, probably unconsciously) as you move your eye away from the original source. I believe the changing size of the image might be because you are moving from looking at something nearby (the taillight) to something far away (the road in front of you), and so your brain perceives the after-images in front of the road to be smaller in comparison to the other images in front of you. I know that’s a confusing explanation in that last sentence — I can write more if you want — the basic idea is that the brain perceives size to be relative to the distance of an object. The same size object a mile away, your brain knows to be larger in real life (an elephant) than the same size object right near by (a mouse).

Hope that helps!

]]> By: Ave http://blog.sciencegeekgirl.com/2009/02/01/pretty-traces-of-light/comment-page-1/#comment-3996 Ave Thu, 13 Oct 2011 21:23:14 +0000 http://sciencegeekgirl.com/?p=220#comment-3996 I am looking for a specific answer to LED light behavior. On vehicle rear lights, some are being made with LEDs now. While driving on the highway one night, I was passed by a vehicle which must have had this type of rear light. Glancing over to the vehicle and then back to my own lane produced a 'repeat trace effect' of the light, with the image getting smaller along the trajectory. The image of the rear lights repeated itself about 20 times along a swoop shape (similar to the Nike swoop), and then disappeared. This image lasted only briefly, but certainly long enough for me to remark on it and attempt (successfully) to repeat the experience, till the vehicle was about half a mile away. I want to know if this is appropriate behavior for this type of light, or should I get myself to the doctor? Thank you. I am looking for a specific answer to LED light behavior. On vehicle rear lights, some are being made with LEDs now.
While driving on the highway one night, I was passed by a vehicle which must have had this type of rear light. Glancing over to the vehicle and then back to my own lane produced a ‘repeat trace effect’ of the light, with the image getting smaller along the trajectory. The image of the rear lights repeated itself about 20 times along a swoop shape (similar to the Nike swoop), and then disappeared. This image lasted only briefly, but certainly long enough for me to remark on it and attempt (successfully) to repeat the experience, till the vehicle was about half a mile away.
I want to know if this is appropriate behavior for this type of light, or should I get myself to the doctor?
Thank you.

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