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
1. Convex Lens
2. Concave Lens
• 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
• Concave lens- the lens is thinner in the middle than at the ends.
Concave lens refracts the light rays so they spread out.
Lens Location Image Size
Convex -far away inverted -small
-close inverted -larger
-very close upright -larger
Concave
-anywhere upright -small
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.
• 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.
• 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.
Refracting Telescope
Reflecting Telescope
Microscope