Ingredients
 | A 2 litre lemonade (soda) bottle |  | A pair of scissors |
 | An interesting light in the ceiling |
Instructions
Cut a roughly circular piece of plastic out of the lemonade bottle, from the part of the bottle just below the neck that is curving in two directions at once. You should end up with a dish shaped piece of clear plastic.
Turn on the light.
Put a piece of white paper on the floor.
Pour a little water into the dish shaped piece of plastic.
Hold it still about 15cm above the paper - move the bowl up and down
Do you see anything on the paper?
Result
You should see an image of the light projected onto the paper on the floor - you have built a camera. If you are too close, too far away or if you squeeze the bowl out of shape the image will go fuzzy, if you look through the water it should act like a magnifying glass.
Explanation
When you pour water into the plastic bowl the water takes on the shape of the bowl, because it is a liquid.
This shape is roughly the same as the shape of a lens or a magnifying glass. This means that most of the light leaving one point on the light which hits the water will be bent so that it goes through a single point on the other side of the lens.
Each point where the light starts will end up in a different point below the lens, so if you put a piece of paper there all the points projected onto the paper will form an image.
If you want to find out more about this see the
Camera Obscura and
Pinhole Camera experiments.
Why is the image not perfect?
Surface tension means that the top surface of the water is actually not flat, which will mean that light is sent in the wrong directions at the edges. Also, the shape of the bottle is only roughly the right shape to make a lens, it is designed to hold lemonade not focus light, but it does a pretty good job despite this.
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