the most important being that with a mirror, light is reflected, while with a lens an image is formed by light that is refracted by, and transmitted through, the lens.
(the most important; being; that) (light; is reflected; ) (an image; is formed; by light) (light; is refracted; ) (light; transmitted; )
the most important light an image light light
being is reflected is formed is refracted transmitted
that
by light