On 1/6/2019 1:56 PM, agrayson2...@gmail.com 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

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