Kitchen Science Magic! When a Stirrer Becomes a Wand — The Mysterious Lens That Flips Up and Down

I’m Ken Kuwako, your Science Trainer. Every day is an experiment.

Do you have a glass swizzle stick or a clear pen lying around in your kitchen or on your desk? What looks like a simple rod might actually be a magic wand that flips the world upside down. When we learn about how lenses work in science class, we often use the structure of a camera as an example. However, the lenses that are truly closer to our daily lives are hidden in the perfectly round water droplets glistening like jewels on a leaf after the rain, or in the marbles you might find at a festival stall.

If you peer at a leaf through a water droplet, the veins look dramatically magnified. If you look at your finger through a marble, your fingerprints look gigantic, like a maze. These “everyday discoveries” are the gateway to science. When I talk to my students, they are much more excited by the real-life experience of “My fingerprint looked huge through the water!” than by precise camera diagrams, and they report back with shining eyes, “Teacher, I saw it!”

Today, let’s explore the surprising lens power held by a glass rod (or a glass swizzle stick) —items you can find right in your school science lab or home kitchen.

The Science Recipe: An Experiment to Invert the World

What you need: A glass rod (or a transparent cylindrical swizzle stick), and text printed upside down.

The Experiment and the Surprising Result

First, prepare an image with arrows or text like the one below, and place the glass rod horizontally on top of it. A phenomenon that is slightly different from a regular lens will occur.

Let’s place the glass rod horizontally over the arrows pointing in four directions. What do you see?

Take a look. Of the arrows that were originally pointing “Up, Down, Right, and Left,” which ones changed direction? That’s right—only the vertical directions were flipped, resulting in Down, Up, Right, and Left. The horizontal directions (right and left) remain the same, but the vertical direction is inverted. This is the work of a cylindrical lens.

Next, try placing it over this “weird text” that looks unreadable at first glance.

What happens to the text?

Strangely, the lines that looked jumbled overlap, and the text becomes clearly readable. The letters, which were intentionally written “vertically inverted” beforehand, are flipped back again by the lens effect of the glass rod, allowing our eyes to see them correctly. The key here is the vertical inversion, which is different from a mirror image. There is a real sense of satisfaction, like solving a visual trick.

The Magic of Magnification Created by the Focal Point

Here is where it gets even more interesting. If you bring the glass rod into tight contact with the paper, the visual effect changes completely.

The change might be subtle in the picture, so please watch the smooth transition in the video:

Did you see it? As you bring the glass rod closer to the paper, the text no longer flips but is simply greatly magnified. This happens because the text has entered inside the focal point (the point where light rays converge) of the glass rod. At this distance, our eyes are viewing a virtual image—the same kind of image you see through a magnifying glass—rather than a real image.

Isn’t it amazing that you can dynamically experience the mechanism of light refraction and focal points with a single glass rod found in your everyday life? By asking “why?” and actually trying it out, your view of the world will gradually change. Grab a swizzle stick from your kitchen and try to decode a secret message! (By the way, you can easily create vertically inverted text using software like Windows Paint by writing the text and then using the “Flip Vertical” function.)

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Make the wonders and fun of science more accessible! We provide easy-to-understand tips and fun science experiments you can do at home. Feel free to search around! ・The content of our Science Notes has been published in a book. Find out more here ・About the operator, Ken Kuwako: here ・For various requests (writing, lectures, science classes, TV supervision, appearances, etc.): here ・Article updates are distributed on X!

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