From Grand Illusions.

Tim goes high tech!

Drop the ultra-strong magnetic ball inside the copper tube, and experience just how slowly the ball falls. Although the ball is not touching the sides of the copper tube, you can still feel the weight of the magnetic ball within the tube. How does it work? The scientific principle is called Lenz’s Law. Unlike iron, copper isn’t attracted to magnets, but it is an excellent conductor of electricity. When the magnet moves inside or near the copper tube, it induces an electric current within the tube. This current acts like an opposing electromagnet, slowing the motion of the magnetic ball and causing it to fall gracefully. These phenomena are what you will see in the Flux Original – https://www.grand-illusions.com/collections/magnetic-toys/products/flux-original

This new version of the Flux Original, the Flux VISION, does something extra. It is wrapped in a specialized magnetic viewing film that uses advanced nanotechnology to visualize magnetic fields in vibrant, hologram-like colours. This film contains magnetic nanoparticles that rearrange themselves in response to a magnetic field. As the magnet glides through, the film reveals the hidden beauty of magnetic fields in hologram-like colours — a breath-taking dance of light that is as scientific as it is stunning.

The spacing between these nanoparticles is on the scale of visible light wavelengths. As the strength of the magnetic flux compresses the particles, different colours emerge, revealing stunning tones that encode valuable information about the magnetic field’s intensity.

Additionally, the nanoparticles rotate to align with the magnetic field direction. This alignment creates distinct visual effects: light stripes appear where the magnetic flux runs parallel to the film, while the most vivid colours emerge when the flux is perpendicular. At intermediate angles, more light is absorbed, producing darker regions.

See https://www.grand-illusions.com/collections/magnetic-toys/products/feel-flux-vision