Ned Yoxall
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 Dec 3 awarded Notable Question Mar 20 awarded Revival Dec 20 awarded Tumbleweed Dec 20 comment Explosively Pumped Flux Compression Generator = EMP strong enough to destroy my phone from a mile away? A couple of extra thoughts that I didn't consider in the above - the duration of the pulse may also be important in terms of the total energy delivered, and the phone's circuitry will probably couple effectively to the pulse at a number of different frequencies (i.e. more energy absorbed meaning more likely to damage the phone). Dec 20 answered Explosively Pumped Flux Compression Generator = EMP strong enough to destroy my phone from a mile away? Dec 13 asked Boundary Condition for Generating Evanescent Waves Dec 3 answered Exciting Surface Plasmon-Polaritons with Grating Coupling Dec 3 awarded Supporter Oct 25 awarded Popular Question Jul 25 comment Is it possible to surpass the diffraction limit for telescopes? Fundamentally, no. But that's not to say that you can't guess at what a star looks like (based on lots of stars you've looked at before), and use image processing to get you closer to the probable reality. At a basic level though, you'll just be making assumptions about what the object "should" look like if you start fiddling with it digitally. Jul 25 awarded Revival Jul 24 answered Is it possible to surpass the diffraction limit for telescopes? Jul 23 revised Parseval's Theorem on a Random Signal added 125 characters in body Jul 23 awarded Editor Jul 23 revised Parseval's Theorem on a Random Signal Added detail about the DC component so that the definition still holds when there's a DC offset. Jul 23 comment Dipole moment induced in a spherical particle And so it depends on the size of your sphere - if it's big, the equation won't hold, if it's small compared to the rate at which the field changes so that the field is "quasi" homogeneous (at least from the sphere's point of view), then it will be valid. If you're sphere is big, things get complicated very fast so good luck! Jul 23 awarded Commentator Jul 23 comment Dipole moment induced in a spherical particle As for the dielectric constant, a perfect conductor does indeed have epsilon as negative infinity. Actual metals tend to have large negative values (say around -1000). In any case, the fraction cancels to 1 (or near as dammit) and so you're just left with $4 \pi r^3$ - in other words the induced dipole depends on the volume of the sphere (makes sense) and the strength of the applied field (also makes sense). Jul 23 comment Dipole moment induced in a spherical particle Ah yes, sorry - I've always thought about this in relation to light. In your case with static fields, the equation above should always apply. The problem with light is the varying field meaning that if the particle is sufficiently large, the field could be pointing one direction on side of it and the opposite direction on the other side of the sphere. Not a problem for you though so the expression should always hold. Jul 23 awarded Student