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Here's a fun little experiment the kids and I did with the kids the other day to demonstrate the reflective property of light. We used a stream of water to capture and bend a laser beam. It's the same principle as the fiber optic cable. This experiment is simple to do with even young kids, if you prepare the bottle beforehand (see below). You'll need to dim the room for best results. I've lightened the photo above so you can see the set-up.
The only specialized equipment you will need is a laser pointer. I have a couple different kinds I bought for our "home lab" last year. I got them from the checkout counter at the supermarket, for around six bucks. (Hey, we're not running on government grants, here!) You can getsomething similar from Amazonfor even less.
Here's how to bend light with water:
Materials
- laser pointer
- stand for laser pointer (we tried poking it through a foam cup and laying it on a stack of coasters)
- rubber band
- clear empty soda bottle with cap
- water
- milk
- permanent marker
- metal skewer
- flame
- masking tape
- sink
Directions:
- Fill the bottle with water and put a few drops of milk in to make it slightly cloudy. You can also try mixing in a little powdered milk or corn starch.
- Wrap the rubber band around the laser pointer so it is pressing the "on" button continuously.
- Set up the laser pointer so it is lying horizontally about 3 or 4 inches from the surface of the counter. Put it next to the bottle and adjust until you see the line of light passing through the milky water.
- With the marker, make a dot where the light beam touches the far side of the bottle. Pour out all the water.
- Heat the metal skewer in the flame (such as a stove burner) until it is very hot. Use the tip to melt a small hole in the soda bottle at the dot.
- Cover the hole with a piece of masking tape. Fill the bottle again with milky water. Put the cap on tight.
- Place the bottle on the counter next to the sink. Set up the laser pointer so it is aimed through the bottle at the hole. Take the tape off to see if the light hits the hole. (The water won't come out until you loosen the cap -- try it!)
- When everything's arranged, loosen the cap until you get a stream of water pouring into the sink. Adjust the laser pointer or walk around the bottle until you can see the light in the curved stream of water.
You can find out more about the science behind this experiment, as well as more simple science tricks, at my family's blog Integrated Science at Home.
