This project allows you to measure how much objects are enlarged in a magnifying glass. On a small strip of masking tape, make measurements using a ruler. These can be as small as 1/16 of an inch. Place the masking tape ruler across the lens of your magnifying glass. Using another ruler, hold your magnifying glass a certain distance away from a table with a penny on it. Observe with the masking tape how large the penny appears. Record your data. Alter the distance between the magnifying glass and the penny. Take another measurement. Do this a few times for different distances. Place your data in a chart to demonstrate the change in optical size when you move the magnifying glass a set distance.
Use a magnifying glass to do a behavioral study of tiny insects. Observe as many different kinds of insects as you can. You can catch some insects, such as ants, while others, such as house flies, you will have to observe in the "wild." Use your magnifying glass to get a closeup look at your insects. Write down your observations. Look at how they walk, what they do before they eat and how they react when you move too close to them. Record your observations in a chart or table, marking the differences in behaviors between different insects.
This experiment can be dangerous so make sure you have an adult help you. Take two ice cubes and put them in separate bowls. Take them outside with a magnifying glass on a sunny day. Hold the magnifying glass above one of the bowls so that it catches the sunlight. Adjust it so that the beam of light shines directly onto the ice cube. Measure how long it takes for the ice cube to melt. Measure how quickly the other ice cube melts. Record your observations and think about why one ice cube melts faster than the other.
Another impressive science fair project is to make your own magnifying glass. Cut a hole the size of a quarter in a small piece of cardboard or an index card. Attach a clear piece of plastic over the hole by taping its edges. Using a spoon, place one drop of water on the center of the clear plastic. You'll be amazed to see that you now have a functioning magnifying glass. Research why water magnifies objects like a magnifying glass. You can set up your device with water at the science fair as a demonstration.