Compound Microscope, Magnification power, Resolving power, Instrumentation of compound microscope, application of compound microscope

1. MICROSCOPE
R. NITHYA M. Sc., M. Phil., (Ph. D)
ASSISTANT PROFESSOR IN BIOTECHNOLOGY
SRI ADI CHUNCAHNAGIRI WOMEN’S COLLEGE, CUMBUM,
THENI DT, TAMIL NADU, INDIA

2. MICROSCOPE
An instrument designed for the study of objects which cannot
be seen with naked eyes.
Microscope (micros = small; skopein = to see/ to look) means
an instrument to see small things.
It is an inevitable instrument for clinical and research
laboratories.

3. The first microscope was designed by Jenssen and Hans Lippershey.

4. MICROSCOPY
The field of designing and using microscopes to view objects that
cannot be seen with unaided eyes is known as microscopy.
Microscopy has three distinct branches. They are
Optical microscopy
Electron microscopy
Scanning probe microscopy.

5. TYPES OF MICROSCOPE
The microscopes are classified into three types
based on the source of illumination.
They are
Light microscope
Electron microscope
X-ray microscope

6. LIGHT MICROSCOPE
In light microscopes, light is the source of illumination.
They are subdivided into following types.
Simple microscope
Compound microscope
Binocular microscope
Phase contract microscope
Interference microscope
Polarizing microscope
Dark field microscope
Ultraviolet microscope
Fluorescence microscope
Cinematography

7. Compound Microscope
It is an optical microscope.
It is formed by the combination of two simple microscopes (a simple
microscope is formed of only one lens).
Principle
The lenses magnify objects.
It has light source, a diaphragm, an object, an objective lens and an eye
piece.
The light passes through the diaphragm.
The diaphragm gathers the light on the object.
The objective lens produces a real (actual), inverted (upturned – upside
down) magnified image of the object.
The magnified image acts as an object for the eye piece.
The eyepiece produces a virtual (effective, actual) inverted and magnified
image of the object.

8. MAGNIFICATION POWER
The ratio of magnified image to that formed in retina of unaided eye is called
magnification.
Magnification power = Size of retinal image seen with a microscope
Size of retinal image seen with unaided eye
The magnifying power of a compound microscope is the ratio of size of the
final image to the size of the object.
M = Size of final image/ Size of the object

9. TOTAL MAGNIFICATION

11. RESOLVING POWER
The ability of the microscope to distinguish two very small and
closely spaced objects as separate entities is called resolving power of the
microscope.
Resolving power of microscopes depends on the wavelength of rays
and numerical aperture (NA) of objective lens.
The RP of a microscope can be calculated by using the formula –
Resolving power (RP) = ʎ
2 x NA

13. NUMERICAL APERTURE
The resolving power of microscope
can be increased by increasing the size
of numerical aperture.
The NA is the function of the
objective lens in relation to its focal
length.
It can be calculated by using the formula
Numerical aperture (NA) = ƞ sin Ɵ

15. SOURCE OF ILLUMINATION
These two microscopes mainly differ in the source of light they use.
One uses a mirror to converge sunlight
while other uses directly an illuminator.

16. STRUCTURE
The compound microscope has the following parts.
REFLECTING MIRROR
It reflects light on the object.

17. CONDENSER
It gathers and focuses the reflected
light on the object.
The condenser has a diaphragm.
It allows the required intensity
(power, concentration, strength)
of light to pass through.

18. DIAPHRAGM.
Diaphragm is a five holed disk placed
under the stage.
Each hole is of a different diameter.
By turning it, you can vary the
amount of light passing through
the stage opening.

19. NOSEPIECE AND APERTURE
•Nosepiece is a rotating turret that holds the
Objective lenses. The viewer spins the
Nosepiece to select different Objective lenses.
The Aperture is the middle of the stage that
allows light from the Illuminator to reach the
specimen.

20. OBJECTIVE LENS
Metal cylinders attached below the nosepiece and contains especially
ground and polished lenses
It magnifies the object.
Onion cells

21. TYPES OF OBJECTIVE LENSES
LPO / Low Power Objective
Gives the lowest magnification, usually 10x
HPO / High Power Objective
Gives higher magnification usually 40x or 43x
OIO / Oil Immersion Objective
Gives the highest magnification, usually 97x or 100x, and is used cedar wood
oil or synthetic oil for better resolution.

22. EYE PIECE
It magnifies the image produced by the objective lens.

23. BODY TUBE
It is a tube with the objective lens at the lower end and the eye piece lens at
the upper end.

24. COARSE ADJUSTMENT
It moves the body tube up and
down rapidly to correct the distance
from the object to get focusing.
FINE ADJUSTMENT
It moves the body tube up
and down slowly to make exact
focusing.

25. SPECIMEN STAGE
It is a platform with a hole in the centre.
The light falls on the object through the hole.
The slide is placed on the stage.

26. STAGE CLIPS
Stage clips hold the slide firmly on the stage

27. NOSE PIECE
It is in the form of rotating disc having holes for fitting the
objective lenses.

28. INCLINATION JOINT
It permits tilting of upper part
of the microscope to adjust to the
eye level.

29. BASE OR FOOT
The foot keeps the body in position.

30. USES OF COMPOUND LIGHT MICROSCOPE.
• Compound Microscope is used in pathology labs to identify diseases.
• In Forensic laboratories, Compound Light Microscopes are used to
identify presence of minerals or metals in human cells so as to solve
criminal cases.
• Forensic Experts can also find out the origin of a drug by viewing its
component particles under a Microscope.

31. Blood cells Human cell
Plant cell
Paramecia
COMPOUND MICROSCOPE IMAGES