What refers to the number of particles of a substance per unit of volume?

population. population is the number of people or animals in a particular place. an example of population is over eight million people living in new york city.

here is your answer hope i .

one part of the electromagnetic spectrum that arrives on earth as solar radiation from the sun is the visible spectrum. wavelengths of the visible spectrum combine to form what we refer to as

answer - d) ultraviolet radiation.

violet /   380–450 nm / 668–789 thz

violet is number 1 in the chart of visible light.