What is a Lens?
[caption id="attachment_59756" align="alignnone" width="287"]

A lens is a transparent curved device that is used to refract light.
A lens is usually made from glass. There are two
different shapes for lenses. They are called convex and concave.
What is a Convex Lens?
A convex lens is thicker in the middle and thinner at the edges.
A convex lens is also called a converging lens.
A convex lens will focus light and make an image.
The image formed by a convex lens is real and inverted
(and can be bigger or smaller than the object)
unless it is being used as a magnifying glass when
the image will be virtual, upright and bigger than the object.
What is a Concave Lens?
A concave lens is thinner in the middle and thicker at the edges.
A concave lens is also called a diverging lens.
A concave lens will disperse light and make an image
that is always virtual, upright and smaller than the object.