Thin Lens

A lens is a piece of transparent material. Lenses are the most important practical application of refraction. There are many instruments, which use lenses. We use lenses in spectacles, cameras, telescope and microscopes. The human eye also contains lens.
Most lenses made from glass or clear plastic. In terms of structure and function, we can classify into two categories.
1.Converging lens
Converging lenses which are thicker in the middle than at the edge
Types of converging lenses

The symbolize of converging lenses

 The part of Converging Lenses  

 

Construction of rays diagram for converging lenses

1. Rays parallel to the principle axis are refracted through to the focal point (F)
2. Rays passing trough F are refracted parallel to the principle axis
3. Rays passing trough to the center (C) are not deviated

The image formed by a convex lens depends on the positions of the object

A. Positions of object beyond 2F (R III)

    The nature of image is real, inverted, diminished, and placed on oppossite of lens at second room

B. Positon of object at 2F

     The nature of image is real, inverted, diminished, and placed on opposite of lens at 2F

C. Position of object between 2F and F

     The nature of image is real, inverted, enlarged, and placed of lens at third room

D. Posotion of object F and C

     The nature of image is virtual, uprigth, enlarged and placed on the same side of the object