1.The popular "magic eye" posters sold in novelty stores allow you to view a "hidden" three-dimensional figure when you stare at them. Explain how this happens (Hint: think about how retinal disparity works).

2. The moon looks larger when viewed at the horizon level than when it is high in the sky (at zenith), even though it obviously never changes size. Explain how this happens (Hint: think about the Ames room illusion).