How to bend light with water

This article was taken from the April 2013 issue
of Wired magazine. Be the first to read Wired's articles in print
before they're posted online, and get your hands on loads of
additional content by subscribing online.

Amaze people by trapping a beam of
light inside a stream of water, then bending it to your will. Kathy
Ceceri, senior editor of the GeekMom blog at Wired.com
and co-author of Geek Mom: Projects, Tips, And Adventures For
Moms and Their 21st-Century Families, explains how to mimic
fibre-optics using household materials.

You'll need A sink or container to catch the water
A clear, smooth-sided two-litre plastic bottle with cap
A cheap laser pointer
A rubber band
A permanent marker
A metal nail

1. Set up the laser pointer
Light bends as it crosses the boundary between materials of
different density. Start by turning the laser pointer on. If
necessary, wrap the rubber band around the on/off button so it
stays on. Lay the pointer on a box or cup so it's level, about ten
centimetres above the counter.

2. Prepare the bottle
Fill the bottle with water and replace the cap tightly. Shine the
pointer so the light passes through. Mark where the beam touches
the far side of the bottle and make a hole through the mark with
the nail. (It won't leak until you loosen the lid.)

3. Now bend the light
Dim the lights. With the pointer aimed at the hole, unscrew the
cap just enough to let out a thin stream of water. The beam should
travel straight through the bottle and curve downwards with the
stream. You may need to adjust the laser or move the bottle to get
the best effect.