Recent content by Johnny B.

Given any two random tile arrangements in a sliding tile puzzle, is it always possible to find a way to go from one to the other? It's trivial to prove that this isn't true for 2x2 puzzles, but I don't know how to approach the problem for bigger sizes, short of brute forcing it with a computer...

That definitely makes sense. Thanks to all of you for replying!

Check it out: http://imgur.com/EpYQv Where's the trick?

Thanks... So, if I arrange the lens like this EYE ------- LENS ------- OBJECT as when looking through a magnifying glass, the image forms between my eye and the lens and I can see it because there are rays going through my eye. Have I gotten it right? What's a "diverging" ray btw...

Homework Statement Diverging lenses produce a "virtual" image, which can be seen but can't be projected, and converging lenses produce a "real" image which can be projected but not seen. How come we can see the image produced by a converging lens, which is supposed to be a real image...