As an owner of a penknife that I occasionally sharpen: It is definitely true that a dull blade gleams, but I am not sure if it is true that a sharp blade does not.
Sharp edges don’t reflect any light visible to the naked eye, but it’ll show up on an illuminated microscope.
The edge width is on par with the wavelength of light at ~300-500 nanometers at best
As an owner of a penknife that I occasionally sharpen: It is definitely true that a dull blade gleams, but I am not sure if it is true that a sharp blade does not.
Sharp edges don’t reflect any light visible to the naked eye, but it’ll show up on an illuminated microscope.
The edge width is on par with the wavelength of light at ~300-500 nanometers at best