Reshared post from +Carmelyne Thompson

Reverse Arrow Optical Illusion

Look Mah; I can do magic! This is a nice experiment to do with the kids. 

This is simply a demo of refraction: bending of light. #scienceeveryday  

A whimsical example: 
https://plus.google.com/u/0/113881433443048137993/posts/MgCxqhMsngq

Sources:
Gif extracted from: http://youtu.be/G303o8pJzls
Physics Central info on Refraction: http://thekidshouldseethis.com/post/79356632627