You are asked to make some measurements of microwaves using a \"polarizing grid\

Question

You are asked to make some measurements of microwaves using a "polarizing grid" consisting of metal wires.Since an electric field does not penetrate a conductor, linearly polarized microwave radiation will pass through the grid most easily when (more than one answer can be correct): a)The wires are oriented at 45 to the oscillating electric field. b) The wires are parallel to the oscillating electric field, but less than 50% of the radiation is stopped. c)The radiation cannot be stopped by a wire grid at all. d)The wavelength of the radiation is the same as the spacing between wires. e)The wires are perpendicular (at 90) to the oscillating electric field. f)The wires can either be parallel or perpendicular to the oscillating electric field. g)The wires are parallel to the oscillating electric field. h)The radiation can only be stopped by a wire grid if a polaroid is also used. i)The wavelength of the radiation is the same as the width of the entire grid.

Explanation / Answer

Electromagnetic waves which have a component of their electric fields aligned parallel to the wires induce the movement of electrons along the length of the wires. Since the electrons are free to move in this direction and the wave is reflected backwards along the incident beam (minus a small amount of energy lost to joule heating of the wire) For waves with electric fields perpendicular to the wires, the electrons cannot move very far across the width of each wire; therefore, little energy is reflected, and the incident wave is able to pass through the grid. Since electric field components parallel to the wires are reflected, the transmitted wave has an electric field purely in the direction perpendicular to the wires, and is thus linearly polarized. (e)The wires are perpendicular (at 90°) to the oscillating electric field.

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