Concave Lenses:  Enough already on mirrors.  Let’s talk about lenses.

Lenses refract light in a sort of organized way.  The type of lenses that we’ll be looking at are called double spherical lenses – both sides have the same radius of curvature.  Two types:

·       Concave lenses - cave inward

o      Aka: diverging lenses because the light rays always  diverge

o      only form virtual images.   

·       Convex lenses - bulge outward

o      Aka: converging lenses because the refracted rays that pass through can converge.

o      can form real or virtual images.

Diverging lenses. (aka: Concave)  Always produces a virtual image.

1.   The parallel ray is refracted as if it had started out at the focal point on the same side of the lens as it is. 

2.   The ray that goes through the center of the lens is not refracted.

The rays look like this:

Note that the rays all diverge.  This means that you have to do the old back ray tracing thing to find the virtual image.

 Like the one below.

Ok, with some practice you should be prepared to use ray tracing to locate images for mirrors and lenses.