This document discusses different types of microscopes, including their history, parts, uses, and key features. It describes: 1) The early compound microscope invented by Jansen, capable of 3-9x magnification. Compound microscopes can magnify 40-1000x and have a resolution of 0.25um. 2) Electron microscopes, which use electron beams rather than light and have much higher resolutions of 1-10nm. Scanning electron microscopes provide 3D images while transmission electron microscopes have higher magnification but only show black and white 2D images. 3) Other microscope types like binocular, darkfield, and phase contrast microscopes and their applications in biology research. Pre

1. University of Sindh Jamshoro
Name: Rimsha Pahore
Group: Group B
Subject: Biological Techniques
Assignment topic: Microscope and its Types

2. Microscope and its Types
The word microscope taken from Ancient Greek Language means small and scope
means to see, it is an instrument used to see small objects that are too small to be
seen by the naked eye.
Simply a microscope is an instrument that produces an accurately enlarged image
of small objects.
Early Microscope
The first microscope is invented by Jansen by mounting two lenses in a tube and
the objected lens is positioned close to the object and produces an image that is
picked up and magnified further by the second lens, called eye piece.
Variables used in Microscopy:-
 Magnification: Degree of enlargement. No of the times the length or diameter
of an object is multiplied.
It depends upon optical tube length, focal length of objective, magnifying
power of eye piece,
So to find total magnification the magnification of the eyepiece is multiple with
the magnification of the objective lense.
This Early Microscope invented
by Jansen having no tripod and
was capable of magnifying three
to nine times the true size.

3.  Resolution:-
Ability of microscope to separate things is known as resolution. The minimum
distances between two visible bodies at which they can be seen as separate not
in contact with each other. The resolution power depends on the wavelength of
the source, smaller wavelength leads to higher resolution.
 Contrast:-
Contrast means coloring in microscope. The contrast is defined as the
difference in the light intensity between the image and the adjacent background
relative to the overall background intensity. Contrast is important to distinguish
one part of the cell from another.
Compound Microscope (Light Microscope)
Compound microscope also known as biological microscope has multiple lenses
which collect lights from the object and then focus the light into the eye, these
microscope have the ability to magnify in range 40x-1000x very minute objects to
a substantial size, clearly showing the smallest details. And the resolution power of
the compound microscope is 0.25um.
The ocular lense in light microscope has magnification of 10x normal vision.
Around the beginning of the 1600’s through work
attributed of Jansen and Galileo the compound microscope
developed.
Compound microscope also known as light microscope,
because it employs visible light to detect small objects and
enlarge them.

4. Electron Microscope:-
Parts of Light microscope
Eye Piece:- known as ocular this is the
part used to look through microscope.
Base:- It supports the microscope
Objective Lenses:- These are the
lenses use for visualization each lenses
has its own multiplication power.
Arm:- It support the body tube, used
to carry microscope
The adjustment knobs:- These
are knobs that are used to focus
microscope.
Stage- where the specimen usually
mounted onto glass slide for
observation.
Illuminator:- it is the light source
for a microscope, compound
microscope uses a low voltage bulb
as an illuminator.
An electron microscope is a microscope that uses a
beam of accelerated electrons as a source of
illumination, it is a special type of microscope having
a high resolution of images. Provide two dimensional
images.
Electron Microscope
Ernst Ruska (1906-1988) a German engineer and
academic professor, built the first electron
microscope in 1931, and the same principles
behind his protype still govern modern Ems.
Draw Tube:- it is the tube that
separates the objective lense and the
eyepiece and assumes continuous
alignment of the optics.

5. Electron microscope is a technique for obtaining high resolution images of
biological and non biological specimens. It is used in biomedical research to
investigate the detailed inside structure of tissues, cells, organelle. The images
allow researchers to view samples on a molecular level, making it possible to
analyze structure and texture.
Resolution: - As the wavelength of electron is less so it has higher resolution
power as compare to light microscope and have 1- 10nm depth resolution and 1nm
lateral resolution.
Magnification: - The magnification of the electron microscope is 50 million times.
Disadvantages: - the main disadvantage of transmission electron microscope is
that we only get black and white images and TEM are large and expensive, it
requires special housing and maintenances.
Scanning Electron Microscope
Scanning electron microscope used to obtain information about the surface,
topography, morphology and composition and other properties, structural and
chemical information point by point. Extremely small micro organisms like the
anatomical pictures of insects, worms, spores, or other organic structures.
It is the type of electron microscope, invented
by Max knell in 1935 it produces the image by
scanning it with focus beam of electron.
Scanning electron microscope provides three
dimensional images. The magnification of SEM
is less than TEM but its resolution power is
high about 0.4 nanometer.
Scanning Electron Microscope

6. Preparation of Specimen for SEM
1:- Cleaning the surface of the specimen. (it’s important because surface can
contain variety of unwanted deposits, such as dust, slit etc.)
2:- Stabilizing the specimen. ( it’s mostly done by fixation and fixation can be
done by aldehyde, tannic acid etc.
3:- Rinsing the specimen. (in order to remove excess fixative).
4:- Dehydrating the specimen. (Alcohol or Acetone)
5:- Drying the specimen (The sample must be dry otherwise it will destroy in EM)
6:- Mounting the specimen.
7:- coating the specimen. (to increase its conductivity in SEM, typically specimens
are coated with a thin layer of conductive metal gold, palladium, platinum.
Working of Scanning Electron Microscope:-
Electron Source:- Electrons are generated at the top of the column by the electron
source. They are then accelerated down the column that is under vacuum. Which
helps to prevent any atoms and molecules present in the column from interacting
with the electron beam and ensure good quality imaging.

7. Condenser and objective lens: - The electromagnetic lenses are used to control
the path of the electrons. The condenser lens defines the size of the electron beam
which defines resolution, while the objective lens main role is the focusing of the
beam onto the sample.
Scanning Coils: - After beam is focused, scanning coils are used to deflect the
beam in the X and Y axes so that it scans in the raster fashion over the surface of
the sample.
Different types of the electrons are emitted from the samples upon interacting with
the electron beam. A back scattered electron detector is placed above the sample to
help detect backscattered electron.
Secondary Electron Detector: - it is placed at the side of the electron chamber at
an angle, in order to increase the efficiency of detecting secondary electrons which
can provide more detailed surface information.
Some Pictures under Scanning Electron Microscope
However there are so many uses of SEM but these are expensive and large and
special training is required to operate them and they are only limited to solid
samples. It also carries a small risk of radiation exposure associated with the
electrons that scatter from beneath the sample surface.
Polyester Thread
Red Blood Cells

8. Binocular Microscope:-
A binocular microscope head works by taking one light beam and splitting it into
two parts that then go to the eyes, the prism that does is known as splitter prism.
The main advantage of binocular microscope over monocular is that it has high
magnification power, trinocular microscopes are also available they contain third
eye piece. The third eyepiece of this type of microscope allows you to mount a
camera onto the eyepiece.
Applications of Binocular Microscope:-
 The binocular microscope widely use in scientific laborites to perform
researches.
 The binocular microscope used in application into cell biology, research, blood
microscopy, urine analysis, biotechnology, pathology etc.
Disadvantages of Binocular Microscope:-
The binocular microscope are much heavier and expensive than simple
microscopes, they require a regular maintenance check for smooth functioning.
Binocular Microscope
Binocular microscope is any optical microscope with
two eyepieces to significantly ease viewing and
observe slide samples. Most of the microscope sold
today is binocular microscope

9. Dark Field Microscopy:-
Dark field microscopy is a technique used to observe unstained samples causing
them to appear brightly against a dark, almost purely black background. So there is
no need of staining.
A dark microscopy is used to examine live microorganisms that either invisible in
the ordinary light microscope or cannot stained by the standard methods so there
we can use dark microscopy. Recently dark field microscopy has regained some of
its popularity when combined with other illumination techniques such as fluoresce.
The dark field microscopy can be perform both in light or electron microscope by
blocking the light source causing light to scatter as it hits the specimen.
Applications of Dark Microscopy:-
 Dark field microscopy is used to study marine organisms such as algae,
plankton, diatoms, insects yeast etc.
 To study live bacterium.
 More detailed view of external features, outline boundaries, edges.
 It is used for viewing objects that are unstained, transparent, and absorb little or
no light.
 It’s useful for viewing diamonds and precious stones and minerals.
Bacteria Colony Snow Flake

10. Disadvantage:-
The main disadvantage of dark field microscope is that you need to take special
care that the slide, stage, nose and light source are free from small particles such as
dust, as these will be as part of image, similarly if you need to use oil or water on
the slide, it is almost impossible to avoid all air bubbles.
Phase Contrast Microscopy:-
The phase contrast microscope is a special adaption of the light microscope and
helps to obtain a clear picture of specimen. This microscope allows organelle of
living cell to become visible with fair contrast in them.
Application of Phase contrast Microscopy:-
 Phase contrast enables the visualization of internal cellular components.
 It made it possible for the biologist to study living cells and how they
proliferate through cell division.
Human Cheek cell in Phase Contrast Human Cheek cell in Light Microscope
Phase contrast microscopy is contrast enhancing optical technique that can be
utilized to produce high contrast images of transparent specimen. It was first
describe by Frits Zernike and was awarded noble price in 1953. Samples where
staining is not an option (or might kill the specimen) often utilize phase
contrast.

11. Disadvantage of Phase Contrast Microscopy
The phase contrast microscope is not ideal for thick organisms or particles, thick
specimen can appear distorted. Annuli or rings in contrast microscope limit the
aperture to some extent which decrease resolution.
Camera Lucida:-
It works on simple optical principle reflecting beam of light through a prism and a
plane mirror. The microscope image of the object is reflected by the prism on the
plane mirror and there from the image is reflected on to the plane paper. The
observer moves the pencil on the lines of the image and draws a correct and
faithful figure of the object on the paper.
Before the applications of the photography, the camera Lucida was of considerable
importance to draughtsman. The advantage claimed for it was its cheapness,
smallness, and portability, but nowadays has no more importance.
The word has been taken from Latin which means light
chamber. Camera Lucida is a optical device when attached
with a compound microscope helps drawing microscope
images of objects on paper.
That’s how it works. And was first
invented by William hyde
Wollaston in 1806