Page 272 - text book form physics kssm 2020

Compound Microscope

Made up of two convex lenses with short focal lengths. File
Objective lens has focal length, f and eyepiece lens has
o
focal length, f . Focal length f is less than focal length f . Normal adjustment of a
o
e
e
compound microscope can be
Distance between objective lens and eyepiece lens > f + f .
e
o
done by adjusting the eyepiece
Object distance is between f and 2f . Objective lens forms lens so that the fi nal image is
o
o
the fi rst image, I which is real, inverted and magnifi ed. I formed at the near point of the
1
1
lies between F and the optical centre of the eyepiece lens eye, which is 25 cm away.
e
and becomes the object for the eyepiece lens.
Eyepiece lens functions as a magnifying glass. Eyepiece lens Magnifi cation of compound
forms the fi nal image, I which is virtual, magnifi ed and microscope
2
inverted compared to object O (Figure 6.39).
Normally, eyepiece lens is adjusted so that the fi nal image,
I is at the near point of the observer’s eye to achieve the
2
clearest vision. http://bt.sasbadi.com/p4266

Eyepiece lens
(L )
2

Objective lens
(L )
1
O
F o F e
F o I 1 F e

I Observer
2

Final image
Figure 6.39 Formation of image by a compound microscope

266 6.5.2
266
6.5.2