Meet the 3D Standing Wave Machine: a cool little toy that creates hypnotic standing waves with a simple string. It has 2 motors with adjustable speed and distance. With red, green, and blue LEDs, you will get a cool light show in the dark.
More gadgets like this: here
This is great as a teaching tool or just a fun trippy toy.
**Disclaimer: Our posts may feature aff links. As an Amazon Associate, we earn from qualifying purchases. Please read our disclaimer on how we fund this site.