This Week's Experiment - #243 Water Magnifier
There are many different
ways to do this experiment, but this one is the easiest to make and use that
I could find. To try this experiment, you will need:
water
a piece of clear plastic
a flashlight
You can use just about any piece of clear plastic. I dug through the trash
and found a variety of plastic from the packaging of batteries, food, and
other items that we recently purchased. I also tried a section cut from a
plastic storage bag and it worked well too. Whatever you are using, you need
a piece that is at least a couple of inches square. It needs to be large
enough for you to hold easily when you are looking through it.
In the center of the piece of plastic, put a large drop of water. This water
drop will be the lens for our magnifier. Now we need something to look at.
First try something easy, such as a piece of newspaper. Hold the plastic
with the water drop about an inch above the paper. Look at the text through
the water drop. It should look larger. By moving the water drop up and
down, you can change how much you magnify the type. Experiment with larger
and smaller drops to find the size that works best. Once you have seen that,
try looking at some other things. Compare grains of salt and grains of
sugar. Can you see a difference? Look at your fingertip, noticing the
ridges that make up your fingerprint. Look at some ice cream. (I knew I
could fit it in there somewhere.)
How can a drop of water make things look bigger? As light enters the drop of
water, it slows down. If the surface of the water is curved, the light is
also bent into a new path. The rounded shape of the drop bends the light
outwards. As the light spreads out, the image that you see gets larger. To
see how spreading the light makes the image bigger, turn on the flashlight
and hold it near a wall. When the flashlight is almost against the wall, the
spot of light is about the same size as the end of the flashlight. Hold your
finger in front of the flashlight. You will notice that the shadow of your
finger is about the same size as your finger. Now move the light to about
two feet away from the wall. You will see that the spot of light has spread
out much larger. Put your finger back in front of the flashlight. Just as
the circle of light got bigger, the shadow of your finger is also bigger.
The farther you move the flashlight from the wall, the larger the spot of
light gets and the more you magnify the shadow.
You will also notice that as the spot of light on the wall gets larger, it
gets dimmer. The light is spread over a larger area. The same thing happens
as you magnify an image. The more you magnify it, the dimmer it gets. That
is one of the limitations on how many times you can magnify something before
you can't see it well enough to tell anything.
You will also notice that the image is not very good. If your water drop is
not exactly round, the image will be distorted. It will also distort when
you move the drop, as the water wiggles. As magnification increases, any
distortions are also magnified.
Some of the very first magnifiers used water. There are records from 1000 BC
of people using blown glass globes filled with water to magnify things. If
you have a round flask or vase, you can fill it with water and try using it
as a magnifier. It should work very well. If you happen to have a
magnifying glass, look at the lens and you will find that it is curved, just
like the water drop. You can also try using things besides water. Try a
drop of cooking oil, syrup, or any other clear liquid. Some will bend the
light more than others, which will have an impact on how much they magnify
things. I am sure that if you think about it, you can find several other
ideas to try.
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
krampf@aol.com
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