Someone I know has asked about a certain property of holograms which he said he was shown while he was in school, but i can't figure out why the property should be true. He says that he once saw a video of a demonstration where a light (presumably a laser) was shone through a hologram, and the image could be seen on the wall behind the hologram. This doesn't seem to make sense to me. I thought that a lens would be needed to resolve the image onto a screen. Any help is appreciated!