All Science Fair Projects

Question: How do magnifying glasses make things bigger?

Answer:
Magnifying glasses work because the speed of light is not constant and unchanging. Lots of people think that the speed of light does not change. But it does and that's how magnifying lenses work.

When light goes through the lens, its speed changes. That bends the light and our eyes follow it out to where a larger object should be.

That's the other thing we usually misunderstand. Magnifying glasses do not make things bigger. Instead they make things seem bigger.

Bending Light

WHAT YOU NEED:
Toy car or truck - flat piece of cardboard (about 24" X 24") - glue - salt or sugar

WHAT TO DO:
Spread glue over one half of the cardboard and pour on the salt or sugar. Let it dry and lightly brush away the extra. Tilt the cardboard up about 6 inches and roll your car or truck at an angle down the ramp.

What happened to the car's path? Is it a straight line?

Try it with another piece of cardboard that is clean. Compare the two.

Path A
When the car slows down, its path will bend.

Path B
It would take this path if its speed didn't change.

WHAT IS GOING ON:
You built a model of a beam of light (the car or truck) changing speed and bending its path.

Light is not a car or truck. But light does behave something like your model. As soon as the speed of light is changed by the lens, it changes its direction slightly.

Bigger & Better

1. Light from the fly travels in straight lines in lots of directions. Some of them are aimed at the lens.

2. The speed of light is slowed a bit by the lens. That steers it in a new direction when it enters and leaves the lens.

3. The steered beams of light all meet at a place called the focal point. If you move behind the focal point, the light beams criss-cross and the image looks upside-down and backward.

4. Your eyes and mind follow the light back down as though the lines were straight and unbent. That makes it look as though the fly is huge.

P.S. from Jax: Virtual is a word we hear buzzing a lot these days.It's based on the Latin word for truth. But it means: fake or false.

P.S. from Beakman: When people say that the speed of light is constant and unchanging, they're talking about the speed of light through a vacuum. That's about 186,000 miles a second, and it doesn't change. Ask someone who watches a lot of TV to explain what a vacuum is.