Light is something that not many people thing
about: we notice it every day, not really thinking about it. For
us, light is vital, as it helps us see and is critical in the
process of growing food, which we need. One of the properties of
light is that when it goes through a transparent object, it gets
refracted. This means that when the light goes goes from a
medium of specific density to another medium of a different
density, it's velocity changes along with its magnitude. This
property is is useful because this varying degree of refraction
can be used to calculate the density of objects.