Lenses can be either convex or concave, with convex lenses focusing light rays at a focal point while concave lenses refract light rays to spread them out. The location and size of an image produced by a lens depends on whether it is convex or concave and how close or far the object is. Lenses are used to correct vision problems like farsightedness and nearsightedness, as well as in optical devices like telescopes and microscopes.

1. Lenses

2. Lens - a transparent material with at least 1 curved surface that causes light rays to bend, or refract, as they pass through. There are 2 types of lenses Convex Lens Concave Lens

3. Convex lens- the lens is thicker in the middle than at the edges. Convex lens focuses the light rays at the focal point. Focal Point Focal Length

5. Concave lens- the lens is thinner in the middle than at the ends. Concave lens refracts the light rays so they spread out.

7. Lens Location Image Size Convex -far away inverted -small -close inverted -larger -very close upright -larger Concave -anywhere upright -small

8. Uses of Lenses Farsightedness - when you can see distant objects clearly but can’t bring nearby objects into focus. -The eyeball’s lens isn’t curved enough so you need a convex lens.

10. Nearsightedness - when you can see nearby objects clearly but can’t bring distant objects into focus. -The eyeball’s lens isn’t flat enough so you need a concave lens.

12. Refracting Telescope- uses 2 convex lenses to gather and focus light from distance objects. Reflecting Telescope- uses a concave mirror, a plane mirror and a convex lens to collect and focus light from distance objects. Microscope - uses 2 convex lenses with short focal lengths to magnify small objects.

13. Refracting Telescope Reflecting Telescope Microscope