Page 55 - Physics 10_Float

GEOMETRICAL OPTICS

The projection or converging lens provides a real, large and
inverted image. It must be real to be projected on a screen.
The slide (object) must be placed between F and 2F of
projection lens so as to produce a real, large, and inverted
image. Because the image is inverted, the slide must be
placed upside down and laterally inverted so we can see the
image properly.

3. PHOTOGRAPH ENLARGER
In the case of photograph enlarger object is placed at distance of
more than F but less than 2F. In this way, we get a real, inverted
and enlarged image as shown in Fig. 12.29. The working principle
of photograph enlarger is basically the same as that of a slide
projector. It uses a convex lens to produce a real, magnified and
inverted image of the film on photographic paper.
Bulb
Condenser lenses
Photographic
Projection paper
Film
lens

Object
Fig.12.29: Diagram of photograph enlarger h o 0
(a) d
12.12 SIMPLE MICROSCOPE
Fig.12.30

A magnifying glass is a convex lens which is used to produce
magnified images of small objects. Hence, it is also called Virtual
simple microscope. The object is placed nearer to the lens image Magnifying
glass
than the principal focus such that an upright, virtual and Object
magnified image is seen clearly at 25cm from the normal eye. h i
F h o 0
Magnifying Power
Let be the angle subtended at the eye by a small object (b)
when it is placed at near point of the eye(Fig.12.30-a) . d d o
If the object is now moved nearer to the eye(Fig.12.30-b), the Fig.12.30: Image formation in
angle on the eye will increase and becomes , but the eye will magnifying glass
not be able to see it clearly. In order to see the object clearly,

Not For Sale – PESRP 55