MIT Physics Demo -- Microwave Polarization

A polarized microwave emitter and a polarized microwave receiver face each other on a table. At first, the emitter and receiver are polarized in the same direction (up-down), and all the emitted signal gets received.

When a metal comb in inserted between them, with the teeth pointed down, the signal is blocked. This is because the microwaves are polarized in the same direction that the teeth are pointing, creating small currents in the metal that reflect the microwaves backwards. When the comb teeth are turned horizontally, the signal passes through undisturbed.

When the receiver is turned 90 degrees, no signal is received. However, when the comb is inserted at a 45 degree angle, some signal passes through. This is because light waves are made up of two perpendicular components that add up to form the polarization of the wave. When one component is knocked out, the wave changes polarization.

See the original video and more on MIT TechTV - http://techtv.mit.edu/videos/752

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[freemanx2x]

@m1ndcontroller The triangular signal is used just to modulate the microwave signal ( wich is a sinusoidal wave) to show better the amount of the microwave that passes through the filter to the receiver.. Insted of triungular signal you can use any signal (including your voice) to modulate the microwave carrier wave...think of a radio receiver ...

[Libertarianist]

@Saskachewan Think vectors. A polar filter takes the component vector of the polarized light traveling through it. The polarization changes as the light passes through. So if the filter is perpendicular, the component vector is 0. If it's 45 degrees off, only about 70% of the light passes through. Another 45 degree change results in half of the original light making it through both.

[DeductiveReason]

Dear Sir, I have an immense amount of problem with white noise and an alternating sound in my home. There is a tower of some sort across the street from me, and I have 7 transformers around my house in a triangle formation. 3 transformers are on the East side, 3 are on the West side and one on the South side. Would a metal comb like the one in the film, only much larger solve my problem in your opinion?

[Saskachewan]

The most interesting part is from 0:50. How the hell the polarizer (metal comb) can "unpolarize" the waves to make it reappear again? o_O Can someone explain it for me?

[Kywdo]

!!!

[tannersword1]

yea but ummm... you dont think that the signal was modulated with a triangle wave form?

Hah if MIT is spreading lies then I'm not sure I want to know the 'truth' ...your truth, that is

[drewschkelton]

cant you delete this guys comments?

[m1ndcontroller]

WRONG WRONG WRONG WRONG WRONG!!!!!!!!

It has nothing to do with the perpedicularity between electric and magnetic fields!!!!

The wave is polarized because it was PASSED THROUGH A WAVEGUIDE!!!! Yeah, you know that funny looking cone thing on the end of the magnetron?? It has NOTHING to do with the nature light itself!! Which could NEVER EXHIBIT A TRIANGULAR WAVEFORM!!!

MIT spreading lies AGAIN!!!!!!!!

MIT spreading lies AGAIN!!!!!!!!

[waziri]

wat the fuck was the point of that?

[carl95125]

What is the output power and frequency of the microwave emitter? And does it use a Gunn diode?

Thanks, Carl