Notice something odd about the turtle’s head?
There’s nothing wrong with our little mud turtle, he didn’t get decapitated just prior to this photo being taken! His head looks detached from his body for another –less macabre– reason: refraction.
Refraction is why, when you look through or into water, objects aren’t exactly where you expect them to be. Light travels at different speeds through solids, liquids and gasses. With water, light travels 3/4 the speed as it does through air. So when you’re looking at something like a turtle with its head sticking out of the water, you see the turtle’s head in one place, and its body in another.
Want to check out this effect yourself? Put some water in a glass and drop in a pencil or pen. Look at the glass from the top and from the side. The “broken pencil effect” is an easy way to explore refraction at home!