PDA

View Full Version : Question about color/light



DavidP
05-26-2008, 09:55 PM
We recently had a fairly long discussion about the color spectrum, light, and pigments about a month ago. I was thinking about that today as I was driving my car.

As I was driving my car home today I passed an intersection with flashing yellow lights. It was dusk, and as I approached these flashing yellow lights, I looked right at them. To my surprise, for a split second they looked red. I was surprised by this, and decided to look again at the next set of flashing yellow lights. Again: for a split second they looked red as I approached them in my car and looked directly at them. (I was going approximately 80 miles per hour on a highway).

Can anyone provide an explanation for this? All light travels at the same speed, and so I see know reason why the light with red wavelength would reach my eyes at a noticeably sooner time than any of the other wavelengths. Is there any kind of optical illusion going on here?

SlyMaelstrom
05-26-2008, 10:16 PM
I think it mentioned something about yellow lights looking red as you approach them in my driver's education manual. Stop running red lights before you kill someone. :p

indigo0086
05-26-2008, 10:21 PM
You're a Cylon.

Thantos
05-26-2008, 10:37 PM
We recently had a fairly long discussion about the color spectrum, light, and pigments about a month ago. I was thinking about that today as I was driving my car.

As I was driving my car home today I passed an intersection with flashing yellow lights. It was dusk, and as I approached these flashing yellow lights, I looked right at them. To my surprise, for a split second they looked red. I was surprised by this, and decided to look again at the next set of flashing yellow lights. Again: for a split second they looked red as I approached them in my car and looked directly at them. (I was going approximately 80 miles per hour on a highway).

Can anyone provide an explanation for this? All light travels at the same speed, and so I see know reason why the light with red wavelength would reach my eyes at a noticeably sooner time than any of the other wavelengths. Is there any kind of optical illusion going on here?

Perhaps it has to do with the method being used to generate the light. It could be that the red part is generated first prior to the green part. /shrug

SlyMaelstrom
05-26-2008, 10:57 PM
Perhaps it has to do with the method being used to generate the light. It could be that the red part is generated first prior to the green part. /shrugOr perhaps at a specific angle there was something obstructing the green light completely. Though, I'm pretty sure all of those traffic lights are just white light with colored covers in front of them. I could be wrong, though.

zacs7
05-26-2008, 11:00 PM
Or the windshield of your car bent the light :)

Try hang your head out the window and see if it still happens :D

hk_mp5kpdw
05-27-2008, 05:38 AM
If you were moving away from the light at about .215c then a yellow light (~510THz) would appear red (~420THz). Come on, you can tell us, were you speeding away? ....really fast? :D

PING
05-27-2008, 06:21 AM
why the light with red wavelength would reach my eyes at a noticeably sooner time than any of the other wavelengths.

Considering speeds of 80 mph, i don't think you would have any problems with red light traveling faster or yellow traveling slower . Also, color you perceive is because of the difference in wavelengths. Lower the wavelength, higher the frequency, so the speed of all kinds of lights remains constant.

twomers
05-27-2008, 06:40 AM
You ever take acid? Maybe you were tripping...

CornedBee
05-27-2008, 08:38 AM
I think searching the physical side of things is the wrong approach. It's got to be an optical illusion.

abachler
05-27-2008, 07:56 PM
Here is the explanation

http://www.amazon.com/Abnormal-Psychology-13th-James-Butcher/dp/0205459420/ref=pd_ybh_7?pf_rd_p=280800601&pf_rd_s=center-2&pf_rd_t=1501&pf_rd_i=ybh&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0AV7H3ZGQX23Y2KMV5PZ

dwks
06-04-2008, 01:30 PM
I'd be inclined to think that you were looking at lots of green-coloured objects just before you looked at the light, so in contrast the yellow light looked red. Kind of like sticking your hand into cold water, and then into room temperature water. (It feels hot.)

Your speed almost certainly had nothing to do with it.

Thantos
06-04-2008, 01:35 PM
That pound of reefer he had right beforehand probably didn't help either ;)

SlyMaelstrom
06-04-2008, 01:42 PM
That pound of reefer he had right beforehand probably didn't help either ;)Littering and...

Yarin
06-04-2008, 05:52 PM
I bet it had to do with the lighting method. You said it was flashing, meaning it was on a capacitor, and it was most likely led lights, so I'm guessing what's happening is when the capacitor initially lets out the electricity, it's frequency is off a little, causing the led to mimic the effect.

brewbuck
06-04-2008, 08:54 PM
I bet it had to do with the lighting method. You said it was flashing, meaning it was on a capacitor, and it was most likely led lights, so I'm guessing what's happening is when the capacitor initially lets out the electricity, it's frequency is off a little, causing the led to mimic the effect.

An LED is never going to emit anything but a single frequency (okay, a really, really tight band of frequencies). It's either conducting, and emitting light at that frequency, or it's not.

I'm with CornedBee on it being some kind of illusion.