 The significance of the Nerf video showed that the Nerf gun was acting as the x-ray tube. The darts were shooting out, they were the photons, the x-ray shooting out at the target, and the target was that thing that was stuck on the whiteboard, and the photons stuck when they hit around the outside of the target, but when they hit the target itself, that dropped off. And that's because the target's either absorbed the photon or it's scattered it. So what you're seeing there is not the target itself, but the after image, the shadow left by the target, but the x-rays that have gone all the way through to the film or to the detector actually developing the image there. So that's the area that'll go darker. And it is the target itself that would be a region of lightness. Now in the case of your bones in a hand, it's the same principle except that you're not using visible light now. You're using x-rays which have the ability to penetrate in different ways. Okay, the next demonstration is one using fluorescent paper and it'll create an after image.