On Sunday, January 6, 2019 at 11:39:03 PM UTC, Brent wrote: > > > > On 1/6/2019 1:56 PM, [email protected] <javascript:> wrote: > > > > On Sunday, January 6, 2019 at 7:53:52 AM UTC, Brent wrote: >> >> To measure small things you need comparably short wavelengths. If you >> make a photon with a wavelength so short it can measure the Planck >> length it will have so much mass-energy that it will fold spacetime >> around it and become a black hole...so you won't be able to use it to >> measure anything. >> >> Brent >> > > TY. That's clear enough. But there's a related question I was unable to > explain to a friend recently. Suppose we have a small spherical cork > floating on a lake, and we introduce a wave disturbance. If the wave length > is much larger than the diameter of the sphere, it will just bob up and > down as the wave passes. But if the wave length is comparable to the > diameter, the wave will be partially reflected. What is a good *physical* > argument for the existence of the reflected wave, tantamount to a detection > of the cork? I am at loss to offer a physical explanation. TIA, AG > > > When the wavelength is on the order of the cork dimension or smaller the > cork can't react to the wave as if it were just part of the water. Because > of its extent it cannot move with the water at all points, so there are > pressure gradients around the cork which become the source of scattered > ripples. > > Brent >
Thank you, but I am unable to intuit the physicality of those pressure gradients and their wave length dependencies. I think I need to look up how scattering amplitudes are calculated to see the wave length dependencies for scattering. I don't recall it being done in my classical or quantum physics courses, a long long time ago, in a galaxy far far away. AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
