Demonstrating refractive index

[I]f the refractive index of two mater­ials is the same, as is the case for sun­flower oil and Pyrex, then light doesn’t bend at all, and you end up with the nice effect demon­strated [in the video]

More superhydrophobic fun

Superhydrophobic Coating Allows Boiling Water without the Creation of Bubbles

Water can be made to boil without any bubbling if a boiling surface is specifically treated so that the vapor cushion does not break down. This is linked to the Leidenfrost effect.

Acoustic Levitation of Liquids Looks Like Magic

No magic show: Real-world levitation to inspire better pharmaceuticals

The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave.

The speed of sound is about 340 m/s, so a 22 kHz wave has a wavelength of about 1.5 cm; the nodes would thus be half that distance apart, but you wouldn’t have to fill every node. Notice the effect at 0:30, where the standing wave is adjusted — you can see the drops move up and down, in tandem.

This seems to be analogous to a dipole force trap in atomic physics. If that’s so, you’d have a radial pressure gradient also giving confinement, which might account for the somewhat strange look to the speakers.

Operation of a flip-flop memory. After colliding with the droplet in the bistable depression in the middle, the incoming droplet lands to the other possible position in the depression in an alternating manner. Thus, the triggered output alternates between the two output channels. Real time.

Note the (mostly) elastic collision; in a head-on collision of particles of equal mass, the incoming particle comes to rest, while the target is ejected at the same speed as the oncoming particle.