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 Spanish - Chinese The Optics Book - G.O. and thin lenses Written by:Karen
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Related Articles:

Converging Lens Applet
Diverging Lens Applet
Diverging Mirror Applet
Forum

In this section:

The Optics Book

1. Before Optics
2. Light and Illumination
3. Reflection and refraction
4. Geometrical Optics and thin lenses

Thin Lenses
Ray Diagrams
Equations
Mirrors
Practical Aplications

5. The human eye
6. Optics instruments
7. Scattering & spectrum
8. Color
9. Interferences & difraction
10. Polarization
11. Quantic Optics

# Thin Lenses

In order to understand lenses, one must first define some terms.

Some Definitions

• The Focal point is the location at which rays parallel to the optical axis of an ideal mirror or lens converges to a point.
• The focal length is the distance between the focal point and the middle of the lens.  It will be represented by F.  You will also see 2F being mentioned.  2F just refers to two times the focal length.
• The distance from the center of the lens to the object will be referred to as do.
• The distance from the center of the lens to the image will be referred to as di.
• A Real Image is an optical image at which rays from the object converge.  It is inverted or flipped upside down.
• A Virtual Image is a point from which Light rays appear to converge without actually doing so.  It is upright or in the same direction as the object.
• A concave lens is a lens thinner in center than edges and is diverging.
• A convex lens is a lens thicker in the center than at the edges and is converging.

 The Optics. Made by Karen, Timothy and, César for ThinkQuest . 1999 - 2000 All rights reserved