Solution:
The question “Can humans ever directly see a photon?” refers to the human ability to detect light particles—photons—with the naked eye. The straightforward answer is no; humans cannot see individual photons directly because of the way our eyes work.Human vision relies on photoreceptor cells in the retina, the rod and cone cells. These cells respond to photons, but they generally require multiple photons to hit in close succession to trigger a response due to their threshold of activation. Under normal conditions, a number of photons are necessary to produce a visual signal that is sent to the brain for interpretation.However, under very controlled laboratory conditions, studies have suggested that the human eye could be sensitive to a small number of photons, potentially as few as just five or six, due to the statistical probability that a few photons would hit the same or nearby rods in a short enough time span to cause a response. This would not be seeing a photon in the sense of resolving it as an individual particle, but rather detecting the presence of extremely dim light. Under everyday circumstances, such an event is exceedingly unlikely, and therefore humans cannot "see" a photon in the common understanding of vision.