| This will give a negative focal length for a convex lens of air inside water. |
| Photograph by Allan Mills of a rectangular grid of lines on a white board, taken using a simple convex lens. |
| A double convex lens with a focal length of 50 cm is fixed in a PVC pipe about 60 cm long. |
| Light enters the human eye via the transparent cornea, the eye's front window, which acts as a powerful convex lens. |
| We saw in the last section that a real image is formed by light moving through a convex lens. |
| In a double convex lens, such as a magnifying glass, the light will bend when it exits as well as when it enters. |
