4. Geometrical Optics and thin lenses
Lenses are everywhere in this world. They are used for glasses,
in telescopes, in photocopy machines, etc. It is therefore important
for us to understand the basic principles of lenses. There are
two types of lenses, converging and diverging. Convex lenses are
converging, and concave lenses are diverging. Keep in mind, that
as Light rays hit the lens, they will bend towards the fatter part
of the lens. This is the reason that a convex lens is converging.
As the Light rays hit the converging lens, they bend towards the
center, which is the thicker part, and the Light rays will cross
with each other.