Let's start with a digital one. It's an animated gif that plays with the persistance of vision creating a green dot where no green dot really is. The instructions are pretty simple - stare at the black crosshairs for a few seconds and see a green dot appear where the pink dots are disappearing. I think you'll have to click on the picture below, because - for some reason - blogger doesn't seem to like animated gif's.
That's a pretty standard one, similar in form to the ones where you stare at an image for a while and then stare at a blank white space and see the negative image. Here's other examples called Queen Elizabeth II or bird in a cage.
I thought about posting links to my favorite optical illusions, but there are just so many that I enjoy. Instead, I'll drop links to a few sites that have bunches and bunches of great optical illusions:
- The Exploratorium exhibit
- Michael Bach's illusions site
- Colorcube's site - from the rockin'ly cool Colorcube (which I have in my classroom)
- Mighty Illusions blog
- Another optical illusion blog
- Wikipedia's optical illusions entry