From Physics in the Pub 2016, a great set from Leon Twardy about sound waves, how microphones work, and how an acoustic guitar steals energy from the future.
The Rubens Tube is a really complicated demo that seems simple. Once you start thinking about it you realise that sound antinodes are points of oscillating pressure, so the flames shouldn’t be stable peaks – they should be going up and down at the frequency of the wave!
And if you change the gas pressure a lot the nodes and antinodes reverse position! Wish I’d thought these points through before Derek asked me to film this!