Refracting telescopes focus light by using a lens, while reflector telescopes focus light by using a mirror.
(Refracting telescopes; focus; light; by using a lens) (reflector telescopes; focus; light; by using a mirror) Context(reflector telescopes focus,List([57, 83))):(reflector telescopes; focus light by using; a mirror)
reflector telescopes focus,List([57, 83))
Refracting telescopes reflector telescopes reflector telescopes
focus focus focus light by using
light by using a lens
light by using a mirror
a mirror