# Tag Info

4

Laser pointer, wire, screen at known distance. You will see the following diffraction pattern: (not trying to make the best image... exposure could have been better, and I could have put a beam stop in in order to avoid the overexposure of the central beam.) The point is that I can see a series of "blobs" that correspond to diffraction peaks from light ...

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copper wires can be measured by using screw gauge. read your text for how to use screw gauge. and use moving microscope to measure the same by optically

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Using optics, you say? Well, you make a Michelson interferometer, with the movable mirror referenced to a mechanical stop. You move the mirror away from the stop, insert the wire and close the gap until the wire is held lightly between the base of the mirror and the stop. Now pull out the wire and slowly close the gap until the mirror makes contact with the ...

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You can also measure the electric resistance of a long piece of the wire and the calculate the cross section of the wire using the fact that the specific resistivity of copper (at 20 C) is $1.68\times 10^{-8}$ Ohm m.

4

The atoms in the lattice can be thought of as coherent re-radiators of the incident photons. This is not unlike the scenario we have in a double slit experiment, where a Huygens construction of the wave front considers each point in the slit as a radiation source. So it might be "opinion" but I think that diffraction is an appropriate word to use.

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You can first measure the length of the wire, then put the wire into the water, and see the volume change of the water. Then use $\pi r^2 = V/L$ to get the diameter. edit If you need more accuracy, maybe you can either coil the wire on a pencil or some other object many times, then you can measure the the length of many diameters, like in this graph. ...

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A micrometer would be the preferred method. A caliper would not be appropriate because it would not give you enough precision.

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Technically Micrometers or more commonly called as Screw Gauge are used to calculate diameter or radius of thin wires in physics labs you can refer to this article: https://en.wikipedia.org/?title=Micrometer

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I don't know what accuracy you need, but you can wind (densely), say, 100 turns of wire on a cylinder and measure the length of the coil. EDIT: another approach (which can be more accurate, if you know what material you have): take a long piece of wire and weigh it. There are some ways to measure density as well.

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Imaginary wavevectors are possible and, as ptomato's answer correctly points out betoken evanescence. I'd like to add a few words to his answer that might help clear up your confusion. Imaginary wavenumbers always betoken Evanescence. Sometimes the vague term "nearfield" is used to connote something not propagating. Evanescence is NOT dissipative; this is ...

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Yes, indeed the out-of-plane component of the wave vector of a surface plasmon is imaginary. A purely imaginary wave vector means the wave does not radiate in that direction, but instead is evanescent. (That's what you get if you plug in a purely imaginary $k_z = -i\alpha$ into the formula  E(z, t) = e^{i (k_z z - \omega t)} = e^{-\alpha z} e^{-i\omega ...

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The electron is an elementary particle. Elementary particles are point particles, no extent. This is a basic postulate in the standard model of particle physics that has been tested over and over again the past fifty year. When experimenting with elementary particles we have to use quantum mechanics. It is proven beyond doubt that classical physics and ...

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