PURPOSE: To show the partial reflection and partial transmission of a wave across the boundary of two media that have different indices of refraction. And to show how impedance matching acts as a buffer to reduce the partial reflection and increase the total transmission of the traveling wave across the boundary of the two media.
DESCRIPTION: There are two different wave machines that have different wave velocities, as shown in the photo above at left. One has long rods and the other has short rods. They can be clamped together directly. when clamped together they create mismatched indices of refraction at thier boundary. When a traveling wave pulse is started by hand at one end of one machine it will show a partial reflection and a partial transmission when it meets the boundary of the two machines.
To show imedance matching, seperate the two wave machines and insert an impedance matching wave machine between them, as shown in the middle photo. The impedance matching machine has a smooth gradient of progressively longer rods, with short rods at one end that match the short rod machine and long rods at the opposite end that match the long rod machine. With the impedance matcher acting as a smooth buffer the abrupt boundary is smoothed between the two different wavelength machines. They become impedance matched together. When a traveling wave pulse is started by hand at one end there is complete transmission and no reflection at the matched interface.
EQUIPMENT: Three wave machines, as photographed.
Updated by Jun Qi in 3/24/2000