Temporary blindness

  1. The other day i was looking at a big illuminated wall on the side of a casino. The light came from inside the wall and changed colors in many different ways. I noticed that when the wall was fully green and then faded to fully red, that i was blind for about 2 or 3 seconds.

    Why would that happen?
     
  2. jcsd
  3. Well, try dipping a hand in hot water and the other in cold water. Now switch. Look at a picture of a streetlight and then look at a white paper. Notice anything different?
     
  4. I should notice that the light wasnt very bright, about the same as a tv.
     
  5. Moonbear

    Moonbear 12,265
    Staff Emeritus
    Science Advisor
    Gold Member

    What Moridin is suggesting is that you consider a phenomenon often called "receptor fatigue" in textbooks, which is a bit of misnomer, as it's actually an adaptation response. When the photoreceptors in the eye are stimulated continuously by one wavelength, your brain starts to "ignore" the signals for that wavelength and only sees the other wavelengths in the visible spectrum. It sounds like somehow, the lights you were looking at were timed just appropriately to fatigue both the red and green responses before fully recovering from the first, so that you were briefly insensitive to most colors.

    Try the example Moridin suggested...don't make assumptions of the results...try it for yourself and see what really happens. You can just draw some large dots on a piece of paper to create the effect without needing a picture of anything in particular. Draw a pattern of four dots...red, green, blue, yellow (or just red and blue for simplicity if all you have are ballpoint pens for drawing in color), stare at it for 20 - 30 seconds, then immediately shift your focus to a blank sheet of white paper.

    The reason he suggests trying the hot and cold water experiment is that the concept is the same for temperature sensation as for photoreceptors, in that you'll experience adaptation (you may have already noticed this if you've spent a lot of time outside on a cold day, and then come inside to wash your hands...have you noticed that even just cold water from the tap feels very hot under those conditions?)
     
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