What Happens When Waves Collide? Explore Superposition with a DIY Scratch Simulator!
I am Ken Kuwako, a Science Trainer. Every day is an experiment!
From the crashing waves at the beach to the soothing melodies in your ears, and even the invisible signals connecting your smartphone—our world is absolutely filled with “waves,” both seen and unseen. Have you ever wondered what happens when two waves traveling from opposite directions collide head-on? Unlike solid objects that bounce off each other, waves possess a mysterious, almost magical quality.
Today, I want to introduce a self-made educational tool that lets you visually experience the wonder of these waves!
The “Wave Merger” Simulator: Conceived on a Commuter Train
There was an educational tool I had been determined to create for a long time: a tool to visualize the “superposition of waves.” I spent my daily commute racking my brain, thinking, “How can I use Scratch to program wave movements that feel truly realistic?”
After much trial and error, I finally finished it! Here is the result:
https://scratch.mit.edu/projects/224259809/
I’ve also uploaded a video of the simulator in action on YouTube. Take a look at how smoothly it moves!
The Magic of Waves: What is the “Principle of Superposition”?
What did you think? In this simulator, you can generate waves whenever you like just by clicking the buttons at the top of the screen.
In science class, we learn about the “Principle of Superposition.” This law states that when two waves overlap, the resulting height at that point is simply the “sum of the heights of each individual wave.”
For example, when a crest meets another crest, they combine into a surprisingly large wave, as shown in the image below. This is called “constructive interference.”
On the flip side, when a crest meets a trough, the waves can cancel each other out, leaving the surface momentarily flat! Modern “noise-canceling headphones” actually use this exact principle. They pick up outside noise and instantly generate an “opposite” wave to cancel it out. Isn’t the power of science incredible?
Peeking into the “Invisible Waves”
The best part of this simulator is that you can “see through” the combined wave to see what’s happening inside.
Even when it looks like one giant wave, the two original waves are still hidden within it. After they overlap, they pass right through each other and continue on their way, completely unchanged. This is known as the “independence of waves.”
This simulator allows you to experiment with many different wave shapes. Whether in the classroom or at home, I hope you’ll have fun playing with it like a puzzle, asking yourself, “What happens if I crash this wave into that one?”
Inquiries and Requests
Bringing the wonder and excitement of science closer to you! I’ve compiled many fun, easy-to-follow science experiments you can try at home. Feel free to explore more!
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Watch experiment videos on the Science Material Channel!
４月のイチオシ実験！
- 光の魔法CMYウォーターキューブ：光の魔法を体験せよ！水を注ぐと新たな立方体が出現する魔法のような実験です。
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- サクセス15 ４月号にて、野球の科学について記事を執筆しました（2026/3）
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- 『きめる!共通テスト 物理基礎 改訂版』（学研）… 高校物理の参考書です。イラストを多くしてイメージが持てるように描きました。授業についていけない、物理が苦手、そんな生徒におすすめです。特設サイトはこちら。
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- 3/20（金） 日本理科教育学会オンライン全国大会2026「慣性の法則の概念形成を目指した探究的な学びの実践」について発表しました。
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- 楽しい実験…お子さんと一緒に夢中になれるイチオシの科学実験を多数紹介しています。また、高校物理の理解を深めるための動画教材も用意しました。
- 理科の教材… 理科教師をバックアップ！授業の質を高め、準備を効率化するための選りすぐりの教材を紹介しています。
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