PURPOSE: To demonstrate polarization of microwaves and the show how microwaves are polarized.
DESCRIPTION: The microwave transmitter and receiver are positioned about 50 cm apart, with both antennas oriented vertically, and the signal is seen using an overhead projector microammeter. Rotate the receiving antenna to demonstrate that these antennas have a direction of polarization associated with them. Q: When the wire cookie cooler grate is placed between the source and the receiver with its wires oriented vertically, what will happen to the microwaves? Will they (a) be attenuated, or (b) pass on through unaffected? What happens when the grate is placed in the beam with its wires horizontal? A: The beam will be attenuated when the wires are vertical and pass through unaffected when the wires are horizontal!
This perhaps counterintuitive result is just the opposite from what one would expect on the basis of the demonstration with rope waves, M7-05: ROPE AND COOKIE COOLERS. Here, the microwaves are attenuated because when the wires are vertical the vertically polarized electric field is absorbed, causing electron currents in the vertical wires. The radiation is re-emitted, but in all directions, so the intensity is attenuated due to solid angle. The iodide crystals with which light polaroid is constructed also absorb the light this way, but the electron currents produced are absorbed in the crystal rather than being re-emitted.
Cross the transmitting and receiving antennas so that no radiation is picked up. Demonstrate the component of a component by holding the wire grate between the transmitter and the receiver at a 45 degree angle.
SUGGESTIONS:
REFERENCES: (PIRA 6h10.20)
EQUIPMENT: Microwave transmitter and receiver with overhead projector meter and wire cookie cooler grate.
SETUP TIME: 5 min.
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