2. LENSESLENSES
Submitted By :Submitted By :
TREESA YESUDASTREESA YESUDAS
PHYSICAL SCIENCEPHYSICAL SCIENCE
N.S.S.TRAININGN.S.S.TRAINING
COLLEGECOLLEGE
PANDALAMPANDALAM
3. In older days, eye glasses were made ofIn older days, eye glasses were made of
thick convex lenses. These lenses resembledthick convex lenses. These lenses resembled
lentil beans. In Latin, lentil beans were calledlentil beans. In Latin, lentil beans were called
‘Lens’. This is how the lens got its name. Mainly‘Lens’. This is how the lens got its name. Mainly
lenses are of two types, convex lenses andlenses are of two types, convex lenses and
concave lenses.concave lenses.
LENSLENS
4. A Convex lens is one whose sides areA Convex lens is one whose sides are
bulged outward . The two surface of thebulged outward . The two surface of the
lens are spherical. Convex lens convergeslens are spherical. Convex lens converges
the light beamthe light beam
CONVEX LENSCONVEX LENS
5. A Concave lens is thin at the centreA Concave lens is thin at the centre
and thicker towards the edges.and thicker towards the edges.
Concave lens diverges the light.Concave lens diverges the light.
CONCAVE LENSCONCAVE LENS
6. The midpoint ofThe midpoint of
lens is called opticlens is called optic
centre of the lens. Acentre of the lens. A
ray passing throughray passing through
the optic centre doesthe optic centre does
not undergo anynot undergo any
deviation .deviation .
OPTIC CENTREOPTIC CENTRE
7. Focal length of a lens is theFocal length of a lens is the
distance between optic centre anddistance between optic centre and
principal focus. Focal length of convexprincipal focus. Focal length of convex
lens is taken as positive, while focallens is taken as positive, while focal
length of concave lens is taken aslength of concave lens is taken as
negative. Focal length is usuallynegative. Focal length is usually
expressed in centimetres or metres.expressed in centimetres or metres.
FOCAL LENGTHFOCAL LENGTH
8. The lens equation isThe lens equation is
1/u + 1/v =1/f1/u + 1/v =1/f
u- Distance of object from optic centreu- Distance of object from optic centre
v- Distance of image from optic centre.v- Distance of image from optic centre.
f- focal length of the lensf- focal length of the lens
LENS EQUATIONLENS EQUATION
9. Power is the reciprocal ofPower is the reciprocal of
the focal length. Its unit isthe focal length. Its unit is
dioptre.dioptre.
That is power, P=1/fThat is power, P=1/f
POWER OF THEPOWER OF THE
LENSLENS
10. Power is the reciprocal ofPower is the reciprocal of
the focal length. Its unit isthe focal length. Its unit is
dioptre.dioptre.
That is power, P=1/fThat is power, P=1/f
POWER OF THEPOWER OF THE
LENSLENS
