This Week's Experiment - #243 Water Magnifier

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.

These experiments are from Robert Krampf - The Happy Scientist

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