text: are photons,mesons etc.manifest or imaginary phenomena? any perceptibly manifest phenomenon by experience should simultaneously satisfy two conditions viz.a magnitude represented by some number of dimensionless ratio or defined units and a characteristic relating to cognitory discriminative qualities(color,tone, smell etc.).a strong beam of light involving photons satisfies both the above conditions such as intensity in lumens /unit area and a discriminating color such as orange,green or white etc. hence answer is sought to identify the related attribute since any phenomenon imagined as a numberless dimension will be in contrast to the manifest and ,therefore,beyond the scope of objective experience. of course they are real particles. photons are used to demonstrate the wave nature of light while mesons are smaller sub-atomic particles found and detected in the atom