Wave moving from one medium to another causes interesting effects! 


Watch the Video: 

And the older version:
 

Teachable Topics:

  • Traveling waves
  • Reflection
  • Impedance Matching

Theory:

If two differently-sized wave machines are linked together, the point where they meet makes an abrupt change of medium for waves traveling along the machine. Waves starting in one medium will move into the other, but at the point where the wave crosses the junction a large part of the wave will be reflected. Fitting a tapered section between the large and small sections of the wave machine makes the transition between the two media more gradual. As a consequence, a wave passing from one medium into the other is reflected much less than before.


Apparatus:

  • Large and small wave machines
  • Tapered wave machine
  • One damper
  • Two small couplings

Procedure:

  • Set up both the large and the small wave machines on a flat surface.
  • Attach the two together with a small metal coupling.
  • Place the damper on the end rod of the small wave machine.
  • Next, flick the last rod of the large wave machine to send a large crest down the rods. When this crest hits the junction between the two wave machines, some of the wave reflects back, while the rest keeps going.
  • Now connect the wide end of the tapered wave machine to the large wave machine and the narrow end to the small wave machine.
  • Keep the damper in the same location, and send another crest down the machine.
  • With the tapered section installed, waves should now reflect less than when they hit the abrupt transition between the large and small wave machines.
Impedance Matching 1
 
Impedance Matching 2