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.
