The wonder and beauty of physics without getting involved in mathamatical jargon
Density is same every where and yet differs
Physics solves old age question of philosophy
That there is no rarefaction and condensation.
h has same magnitude everywere same volume but different shapes .The mass in h is same. What differs is time of unit frequency.
This means every quanta has same density but different everage density on time axis. There might be more quanta in some space and less in some as per time.
But at every quanta place density is same. The situation is same subtleties of speeds may differ and yet each speed has same volume and mass and thus same density. Now there may be different speeds moving together as in case of light .
(proof in equations awaited)