Compound microscope

1. Compound Microscope

2. Hans Lippershey
Zaccharias Hanssen

3. Hans Lippershey
Zaccharias Hanssen

4. A compound microscope is a
microscope with two or more convex
lenses.
A light source is used to illuminate
what is being observed.
There are usually four objective lenses
with magnifications of 4X, 10X, 40X,
and 100X.

5. Head
Arm
Base
Eyepiece
Fine Adjustment Knob
Coarse Adjustment Knob
Stage
Illuminator
Objectives
Revolving Nosepiece
Diaphragm

6. Lenses
• composed of two lenses:

objective = short focal length

eyepiece = focal length of few cm


• lenses separated by some distance greater
than either lens' focal length

7. How does it work?
• object placed outside the focal length of
objective, forms inverted image near focal
length of eyepiece

• eyepiece magnifies the image
• the lenses of a compound microscope
bend the light that you shine from the
bottom through the sample to make it
seem larger. there are two lenses to add
to (compound) the effect

8. Image Formation

•The object (O) is placed just outside F
o
, the principal focus of the objective lens.

•F
e
is the principal focus of the eye lens.

•A real, inverted magnified image I
1
is formed. The magnified image I
1
acts as an object for the eye lens.

•The final image I
2
is virtual and is magnified still further. It is inverted compared with the object.
I
2
may appear 1000 times larger than the object.

9. Magnifying Power
Definition:

Magnifying Power
-the ratio of the size of the final image (I
2
) as seen through the
microscope to the size of the object as seen with a naked eye.

10. Physics behind…
Magnification produced by the objective is given by:
M
o= size of image / size of object
M
o= q
1/ p
1--------------- (1)
Magnification produced by the eye piece is given by:
M
e= size of image / size of object
M
e= q
2/ p
2
M
e= d / p
2--------------- (2)
Using thin lens formula for eye piece :
 1/f
2 = 1/q
2 + 1/p
2
Here f
2 = f
e, q
2 = - d and p = p
2
1/f
e = 1/-d + 1/p
2
1/f
e = -1/d + 1/p
2
Multiplying both sides by "d"
d/f
e = -d/d + d/p
2
d/f
e = -1 + d/p
2
1 + d/f
e = d/p
2
d/p
2 = 1 + d/f
e----------------(3)
Comparing equation (2) and (3)
M
e = 1 + d/f
e--------(4)

11. Total Magnification:
M =M
o X M
e
M = (q
1/p
1)(1 + d/f
e)
In order to get maximum magnification, we must decrease p
1 and increase
q
1 .Thus maximum possible value of p
1 is fo i.e p = fo and maximum possible
value of q
1 is the length of microscope i.e q
1 = L
Therefore the magnification produced by a compound d microscope is
given by:
M = (L/fO)(1 + d/f
e)

12. Sources
• http://www.wisegeek.com/what-is-a-compound-microscope.htm
• http://www.microscope.com/compound-microscope-history-t-4.html
•Serway 
fin. \:D/