Page 56 - Physics 10_Float

GEOMETRICAL OPTICS

we put a convex lens between the object and the eye, so that
the lens makes a large virtual image of the object at near
point of the eye. In this way, the object appears magnified.
The magnifying power in this case will be:

M =
It can be shown that the magnifying power is given by the
relation:
d
M = = 1+
f
where f is the focal length of lens and d is near point of eye. It
is clear from this relation that a lens of shorter focal length
will have greater magnifying power.
Resolving Power
The resolving power of an instrument is its ability to
distinguish between two closely placed objects or point Magnifying glass is a lens that
forms a virtual image that is
sources. larger than object and appears
In order to see objects that are close together, we use an behind the lens.
instrument of high resolving power. For example, we use
high resolving power microscope to see tiny organisms and
telescope to view distant stars.
12.13 COMPOUND MICROSCOPE
Compound microscope has two converging lenses, the
objective and the eyepiece and is used to investigate
structure of small objects (Fig.12.31). Following are some
features of compound microscope:
Eye
Coarse
Eypiece focusing
knob
Body tube
Fine
Objective focusing
turret knob
Arm

Objectives Slide with
Stage specimen
Condenser
Lamp
Base
Fig.12.31: Compound microscope

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