Convex LensConvex Lens

A convex lens curves outward; it A convex lens curves outward; it has a thick center and thinner has a thick center and thinner

edges edges

Principle FocusPrinciple Focus

When a beam of light parallel to the principle When a beam of light parallel to the principle axis passes trough a converging lens it is axis passes trough a converging lens it is refracted so as to converge to a point on refracted so as to converge to a point on the Principle Focusthe Principle Focus

Convex lensConvex lens

F FC

Principle Axis

C = Optical Centre

CF = FC = Focal Length

F = Principle Focus

Kinds of converging lensesKinds of converging lenses

1.Biconvex 3. Convex concave1.Biconvex 3. Convex concave

2. Plano convex2. Plano convex

Ray construction diagrams for Ray construction diagrams for converging lens converging lens

1.1. A ray parallel to the principle axis which A ray parallel to the principle axis which is refracted through the principle focus Fis refracted through the principle focus F

2.2. A ray through the principle focus F which A ray through the principle focus F which is refracted parallel to the principle axis.is refracted parallel to the principle axis.

3.3. A ray through the optical center C which A ray through the optical center C which is undeviated for a thin lensis undeviated for a thin lens

1. 1. A ray parallel to the principle axis which is A ray parallel to the principle axis which is refracted through the principle focus Frefracted through the principle focus F

F FC

2. 2. A ray through the principle focus F which A ray through the principle focus F which is refracted parallel to the principle axisis refracted parallel to the principle axis

F FC

3. 3. A ray through the optical center C which A ray through the optical center C which is undeviated for a thin lensis undeviated for a thin lens

F FC

Images Formed by a convex lensImages Formed by a convex lens

Object between 2F and FObject between 2F and F

Images : real, inverted, largerImages : real, inverted, larger

F FC2F 2F

MagnificationMagnification

Which m = magnification image

s’ = distance of image from lens

s = distance of object from lens

h’ = height of image

h = height of object

'

''

111

ssf

h

h

s

sm

Note : F (positive)

ExampleExample

1. The convex lenses has a focal length of 4 1. The convex lenses has a focal length of 4 cm. An object 6 cm from the lens, If the cm. An object 6 cm from the lens, If the height of an object 2 cm. Calculate height of an object 2 cm. Calculate magnification of image ?magnification of image ?