1. Convex and Concave Lenses

2.  A concave lens is thicker at the edges than it is at the center.  It spreads light waves apart.

3.  The viewfinder of a camera has a concave lens.  That way, you can look in the viewfinder and see what the whole picture will look like.  The image will remain right side up.

4.  Nearsightedness is an eye condition that makes it difficult for people to see things that are far away.  They can only see things near them clearly.  Concave lenses help to correct nearsightedness.

5.  A convex lens is thicker at the center than it is at the edges.  It bends light waves to make them come together.

6.  A convex lens can be used as a magnifier to make an image on a screen.  The lens of a camera is a convex lens, too.  It brings light waves together on the film, producing an image.  The images are upside down.

7.  Farsightedness is an eye condition that makes it difficult for people to see things that are near.  They can only see things that are far away clearly.  Convex lenses help to correct farsightedness.