Compound microscope

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1. Compound
Microscope
By,
Prof. K.P. Mahajan

2. Aim
Study of compound microscope

3. Introduction
A microscope (Greek: mikron = small and scopeos = to
look).
MICROSCOPE: Is an instrument for viewing objects
that are too small to be seen by the naked or unaided
eye.
MICROSCOPY: The science of investigating small
objects using such an instrument is called microscopy.

4. History
1590:ThetwoJanssenbrothersofHolland,FrancisJanssenand
ZachariasJanssen,whowerespectaclemakersbuiltthefirst
operationallightmicroscope.
1611:Keplerbuiltthefirstcompoundmicroscope.
1665:RobertHookedevelopedthefirstlaboratorymicroscope
whichhasamagnificationof14-42X.Heobservedsmallporesin
sectionsofcorkthathecalledcells.
1674:Leeuwenhoekdiscoveredprotozoabyhisselfbuilt
microscopewithmagnificationof270X.Hediscoveredbacteria
forthefirsttime9yearslater.
1905:Zsigmondyinventeddark-fieldmicroscopy.

5. T
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M
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Types of
microscope
Depending on
the number of
lenses
Simple
microscope (
Single lens)
Compound
microscope (
two lenses)
Depending on
number of
eyepiece
Monocular (
single eyepiece)
Binocular (two
eyepiece)
Depending on
source of
illumination
Light or optical
microscope (Uses
optical lens and
light)
Bright field
microscope
Dark field
microscope
Fluorescence
microscope
Phase –contrast
microscope
Electron
microscope (Uses
electron beam)
Transmission
Electron
microscope
Scanning
Electron
microscope

6. Thetermmicroscopecanbesplitintotwo
separatewords,‘micro’and‘scope’,wherethe
term‘micro’meanssmallortiny,and‘scope’
meanstoviewortoobserve.Therefore,a
microscopecanbeunderstoodasan
instrumenttoobservetinyelements.
Theopticalmicroscopeoftenreferredtoas
thelightmicroscope,isatypeofmicroscope
thatusesvisiblelightandasystemoflenses
tomagnifyimagesofsmallsubjects.
There are two basic types of optical
microscopes:
Simple microscopes
Compound microscopes

7. Magnification of compound
microscope
Inordertoascertainthetotalmagnificationwhenviewinganimagewith
acompoundlightmicroscope,takethepoweroftheobjectivelenswhich
isat4x,10xor40xandmultiplyitbythepoweroftheeyepiecewhich
istypically10x.
Therefore,a10xeyepieceusedwitha40Xobjectivelenswillproducea
magnificationof400X.Thenakedeyecannowviewthespecimenat
magnification400timesgreaterandsomicroscopicdetailsare
revealed.
Alternatively, the magnification of the compound microscope is given
by:
m=D/ fo* L/fe
where, D = Least distance of distinct vision (25 cm)
L = Length of the microscope tube
fo= Focal length of the objective lens
fe= Focal length of the eye-piece lens

8. Parts of a Compound Microscope
It consist of 3 major systems
1.Support system: it comprises of stage, base & body tube
2.Illumination system: it comprises of light source or mirror ,
iris diaphragm and a condenser . The light source may be plain
or concave mirror or electrical lamp.
3.Magnification system: it consists of 2 sets of lenses, the one
which is near to specimen is called objective lens. The second
lens through which image is seen is called eyepiece lens.

9. Parts
Ocular (eyepiece)
Objective
Body tube
Arm
Base / Foot
Coarse focus adjustment knob
Fine focus adjustment knob
Stage
Draw tube
Nosepiece
Condenser
Mirror
Diaphragm

10. Head (Body tube)
This is also known as the body, it carries the
optical parts in the upper part of the
microscope

11. Arm
Supportsthebodytube.
Theentiremicroscopeishandledbya
strongandcurvedstructureknownasthe
arm.
Thearmconnectsthebodytubetothe
baseofthemicroscope.

12. Base
Supportsandstabilizesthemicroscope.
Housestheilluminator

13. Eyepiece
alsoknownastheocular.
thisisthepartusedtolookthroughthe
microscope.Itsfoundatthetopofthe
microscope.
Itsstandardmagnificationis10xwithan
optionaleyepiecehavingmagnifications
from5X–30X.

14. Eyepiece tube
itstheeyepieceholder.
Itcarriestheeyepiecejustabovethe
objectivelens.
Insomemicroscopessuchasthebinoculars,the
eyepiecetubeisflexibleandcanberotatedfor
maximumvisualization,forvarianceindistance.
Formonocularmicroscopes,theyarenone
flexible.

15. Objective lenses
Thesearethemajorlensesusedfor
specimenvisualization.
Theyhaveamagnificationpowerof40x-
100X.
Thereareabout1-4objectivelenses
placedononemicroscope,inthatsomeare
rarefacingandothersfaceforward.
Eachlenshasitsownmagnificationpower.

16. Objective lenses
Oilimmersionobjective–100X
Highpowerobjective–45X
Lowpowerobjective–10X

17. Nose piece
alsoknownastherevolvingturret.
Itholdstheobjectivelenses.
Itismovablehenceitcalrevolvethe
objectivelensesdependingonthe
magnificationpowerofthelens.

18. The Adjustment knobs
Theseareknobsthatareusedtofocusthe
microscope.
Therearetwotypesofadjustmentknobs
i.efineadjustmentknobsandthecoarse
adjustmentknobs.

19. Stage
Thisisthesectiononwhichthespecimenis
placedforviewing.
Theyhavestageclipsholdthespecimen
slidesinplace.
Themostcommonstageisamechanical
stage,whichallowsthecontroloftheslides
bymovingtheslidesusingthemechanical
knobsonthestageinsteadofmovingit
manually.

20. Aperture
This is a hole on the microscope stage,
through which the transmitted light from
the source reaches the stage.

21. Microscopic illuminator
This is the microscopes light source, located at
the base.
It is used instead of a mirror. it captures light
from an external source of a low voltage of
about 100v.

22. Condenser
Thesearelensesthatareusedtocollectandfocus
lightfromtheilluminatorintothespecimen.
Theyarefoundunderthestagenexttothediaphragm
ofthemicroscope.
Theyplayamajorroleinensuringclearsharpimages
areproducedwithahighmagnificationof400Xand
above.
Thehigherthemagnificationofthecondenser,the
moretheimageclarity.
MoresophisticatedmicroscopescomewithanAbbe
condenserthathasahighmagnificationofabout
1000X.

23. Condenser

24. Diaphragm
itsalsoknownastheiris.
Itsfoundunderthestageofthemicroscopeandits
primaryroleistocontroltheamountoflightthat
reachesthespecimen.
Itsanadjustableapparatus,hencecontrollingthe
lightintensityandthesizeofthebeamoflightthat
getstothespecimen.
Forhigh-qualitymicroscopes,thediaphragmcomes
attachedwithanAbbecondenserandcombinedthey
areabletocontrolthelightfocusandlightintensity
thatreachesthespecimen.

25. Condenser focus knob
this is a knob that moves the condenser up or
down thus controlling the focus of light on the
specimen.

26. Abbe Condenser
this is a condenser specially designed on high-quality
microscopes, which makes the condenser to be
movable and allows very high magnification of above
400X.
The high-quality microscopes normally have a high
numerical aperture than that of the objective lenses.

27. The rack stop
Itcontrolshowfarthestagesshouldgopreventing
theobjectivelensfromgettingtooclosetothe
specimenslidewhichmaydamagethespecimen.
Itisresponsibleforpreventingthespecimenslide
fromcomingtoofarupandhittheobjectivelens.

28. Working Principle of the Compound
Microscope
Compoundmicroscopeshaveacombinationoflensesthatenhancesboth
magnifyingpowersaswellastheresolvingpower.
Thespecimenorobject,tobeexaminedisusuallymountedona
transparentglassslideandpositionedonthespecimenstage
betweenthecondenserlensandobjectivelens.
Abeamofvisiblelightfromthebaseisfocusedbyacondenser
lensontothespecimen.
Theobjectivelenspicksupthelighttransmittedbythespecimen
andcreatesamagnifiedimageofthespecimencalledtheprimary
imageinsidethebodytube.Thisimageisagainmagnifiedbythe
ocularlensoreyepiece.

29. Whenhighermagnificationisrequired,thenosepieceisrotated
afterlowpowerfocusingtobringtheobjectiveofahigherpower
(generally45X)inlinewiththeilluminatedpartoftheslide.
Occasionallyveryhighmagnificationitrequired(e.g.forobservingbacterial
cell).Inthatcase,anoilimmersionobjectivelens(usually100X)is
employed.
The common light microscope is also called a bright-field microscope because
the image is produced amidst a brightly illuminated field. The image appears
darker because the specimen or object is denser and somewhat opaque than
the surroundings. Part of the light passing through or object is absorbed.

30. Precautions
The objective lenses and eyepiece should be cleaned
with the help of silk cloth and cleaning liquid before
using.
The microscope should not be tilted when working,
using it.
When an object needs to be studied, focus on low
power objective first and then move to high power.
The lower power needs to be left in place after all
observations are completed.
When focusing care needs to be taken to ensure that
the objective lens never strikes the stage or the
slide.

31. Only the fine adjustment knob should be used when the high
power objective is employed.
Cover slip should always be used to cover well-mount
preparations before observation under the microscope is
made.
Do not dismantle the microscope.
When carrying the microscope, always use both hands.
Try to place it in a box after using the microscope.
The concave part of the mirror should be used under dim
light.
Oil immersion lens should never be used without the use of
oil.

32. Result
Study of compound microscope was studied

33. QueshionBank
1.A compound microscope uses
a. 2 lenses b. 1 lens
c. 4 lenses d. 5 lenses
Answer:a. 2 lenses
2. The lens that is within the eyepiece of the light
microscope is called the:
a.scanning b. low power
c. high power d. ocular
Answer:d. ocular
3. A microscope has a 4x ocular lens and a 10x
objective, what is this microscope's total magnification?
a. 4x b. 14x c.40x d.400x
Answer:c.40x

34. 1.What is meant by magnifying glass?
Ans. A simple microscope is also called a magnifying glass
because it produces magnified image ofvery small objects.
2. Where the image is formed in compound microscope?
Ans. The image is compound microscope is formed at the least
distance of distinct vision, which is25 cm for a healthy eye.
3. What is the formula to calculate the magnifying power
of compound microscope?
Ans.Themagnifying power of a compound microscope is given
by:M = L/fo( 1 + d )/fo
Where,
fo= focal length of objective
fo= focal length of eye-piece
L = Length of microscope

35. 4. What is magnifying power?
Ans. Magnifying power as simply magnification produced by
any lens is the ratio of distance ofimage to distance of
object from the lens.
i.e. Magnification = distance of image from the lens /
distance of object from the lens
5. What is an objective and an eye-piece?
Ans. An objective is a lens which is placed near the object,
and eye-piece is a lens which is close tothe eye.
6. What is a compound microscope and what are it
uses?
Ans. It is an optical instrument consists of two convex
lenses. It is used for viewing magnifiedimage of very small
objects.

36. Thank You !!!