If you placed a shot glass and a large pail side by side in a rain storm, which one would collect more water in 5 minutes?

Now, imagine you are not catching raindrops but light particles (photons). Which would collect more light; a small mirror or a large mirror?

A satellite, like any other object, will collect and reflect sunlight. A small satellite will not be catching as much sunlight, therefore it cannot reflect as much sunlight as a larger satellite.

If you have ever observed the International Space Station (ISS) you will notice that it appears much brighter than most of the other satellites you have observed. You are directly seeing the effect of size on the apparent brightness, as the ISS is much larger in size than most satellites currently in orbit.