Resonance

Notes

Many instruments use resonance to create a vibrating column of air with a particular frequency.

For example, in a trombone, the length of the tube can be changed, creating a higher or lower pitched note.

GoPro Music: David Finlayson’s Trombone Silliness (2:15)

 

Resonance in Electronics

Resonance can also be used in electronics to provide power to a passive (non-powered) device.

In 1945, Leon Theremin (inventor of the theremin instrument) used resonance to power the thing, a listening device that ended up in the house of the US Ambassador to the Soviet Union.

This principle is used in modern RFID tags.

RFID Tags (1:19)

 

Demonstration

1. Bunsen burner resonance
   1. Light a Bunsen burner and create a large flame.
   2. Put a long cardboard poster tube over the flame, and listen to the sound.
   3. Put a short cardboard poster tube over the flame and listen to the sound.
   4. Which tube is higher pitched? Why?
2. Cut-off plastic bottle in large beaker
3. Slide whistle
4. Glass bottle with different levels of water