It is that light rays passing from an object through air to an observer always refract (bend) in the direction of increasing air density.
(It; is; that light rays passing from an object through air to an observer) Context(It is,List([0, 5))):(light rays; passing; from an object)
It is,List([0, 5))
It light rays
is passing
that light rays passing from an object through air to an observer
from an object