Number of quanta is observable. You can count photons.
OTOH it does not imply that a photon is a "particle" in the same sense a breadcrumb is, with a well-defined diameter, shape, or borders. It is a portion of energy of electromagnetic field that was sufficient to yank an election from a photo element's crystallic grid.
OTOH it does not imply that a photon is a "particle" in the same sense a breadcrumb is, with a well-defined diameter, shape, or borders. It is a portion of energy of electromagnetic field that was sufficient to yank an election from a photo element's crystallic grid.