Eye Lens

   Convex lens   
Convex lens or plus lens is a converging lens. it may be of biconvex, plano-convex or concavo-convex (meniscus)

         
                                                      1                     2                   3

( Basic forms of a convex lens: 1. plano-convex 2.biconvex;3.concavo-convex.)

identification of a convex lens.
1. The convex lens is thick in the centre and thin at the periphery.
2. An object held close to the lens appears magnified.
3. When a convex lens is moved, the object  seen through it moves in the opposite direction to the lens.
Uses of convex lens.it is use (1) for correction of hypermetropia, aphakia and presbyopia, (2) in oblique illemination (loupe and lens) examination, (3) in indirect ophthalmoscopy, as a magnifying lens, and many other equipments.

image formation by a convex lens.

S. No      Position of the object      Position of the image                  Nature and size of the image 
1.            At infinity                         At focus F2                                Real,very small and inverted   
2.             Beyond 2f1                      Between F2 and 2F2                 Real, diminished and inverted
3.            At 2F1                              At 2F2                                        Real,  same size and inverted
4.             Between F1 and 2F1       Beyond 2F2                               Real, enlarged and inverted
5.            At focus F1                       At infinity                                 Real,   very large and inverted
6.             Between 2F1 and the          on the same side of lens        Virtual, enlarged and erect   
                optical centre of the lens
   
      image formation by a convex lens. table 1.4 and figure 1.31 provide details about the position, size and nature of image formed by a convex lens.