notes

1. THE MICROSCOPE
HISTORY
- Invented by Hans and Zacharias Jensen
- Invented in the 16th century, specifically 1590
- Used more than one lens
- 1609 – Compound microscope.
- 1625 – First use of term 'microscope'
- 1665 – First use of term 'cells'
- 1676 – Living cells first seen.
- 1830 – Spherical aberration solved.
- 1874 – Abbe equation.
1284 – First eye glasses
Salvino D’Armate is credited with inventing the first wearable eye glasses.
1590 – Early microscope
Zacharias Janssen and his son Hans place multiple lenses in a tube. They observe that
viewed objects in front of the tube appear greatly enlarged. This is a forerunner of
the compound microscope and the telescope.
1609 – Compound microscope
Galileo Galilei develops a compound microscope with a convex and a concave lens.
1625 – First use of term ‘microscope’
Giovanni Faber coins the name ‘microscope’ for Galileo Galilei’s compound microscope.
1665 – First use of term ‘cells’
English physicist Robert Hooke publishes Micrographia, in which he coins the term
‘cells’ when describing tissue. The book includes drawings of hairs on a nettle and the
honeycomb structure of cork. He uses a simple, single-lens microscope illuminated by a
candle.
1676 – Living cells first seen
Antonie van Leeuwenhoek builds a simple microscope with one lens to examine
blood, yeast and insects. He is the first to describe cells and bacteria. He invents new
methods for making lenses that allow for magnifications of up to 270 times.
1830 – Spherical aberration solved

2. Joseph Jackson Lister reduces spherical aberration (which produces imperfect images)
by using several weak lenses together at certain distances to give good magnification
without blurring the image.
1874 – Abbe equation
Ernst Abbe writes a mathematical formula that correlates resolving power to
the wavelength of light. Abbe’s formula makes it possible to calculate the theoretical
maximum resolution of a microscope.
1931 – Transmission electron microscope
Ernst Ruska and Max Knoll design and build the first transmission electron
microscope (TEM), based on an idea of Leo Szilard. The electron microscope depends
on electrons, not light, to view an object. Modern TEMs can visualize objects as small
as the diameter of an atom.
1932 – Phase contrast microscope
Frits Zernike develops phase contrast illumination, which allows the imaging
of transparent samples. By using interference rather than absorption of light,
transparent samples, such as cells, can be imaged without having to use staining
techniques.
1942 – Scanning electron microscope
Ernst Ruska builds the first scanning electron microscope (SEM), which transmits a
beam of electrons across the surface of a specimen.
1957 – Confocal imaging principle
Marvin Minsky patents the principle of confocal imaging. Using a scanning point of
light, confocal microscopy gives slightly higher resolution than conventional light
microscopy and makes it easier to view ‘virtual slices’ through a thick specimen.
1962 – Green fluorescent protein (GFP) discovered
Osamu Shimomura, Frank Johnson and Yo Saiga discover green
fluorescent protein (GFP) in the jellyfish Aequorea victoria. GFP fluoresces bright green
when exposed to blue light.
1972 – First CAT scanner
Godfrey Hounsfield and Allan Cormack develop the computerized axial tomography
(CAT) scanner. With the help of a computer, the device combines many X-ray images to
generate cross-sectional views as well as three-dimensional images of internal organs
and structures.
1973 – Electron backscatter patterns observed

3. John Venables and CJ Harland observe electron backscatter patterns (EBSP) in the
scanning electron microscope. EBSP provide quantitative microstructural information
about the crystallographic nature of metals, minerals, semiconductors and ceramics.
1978 – Confocal laser scanning microscope
Thomas and Christoph Cremer develop the first practical confocal laser scanning
microscope, which scans an object using a focused laser beam.
1981 - Scanning tunnelling microscope
Gerd Binnig and Heinrich Rohrer invent the scanning tunnelling microscope (STM). The
STM ‘sees’ by measuring interactions between atoms, rather than by using light or
electrons. It can visualize individual atoms within materials.
1986 – Nobel Prize for microscopy
The Nobel Prize in Physics is awarded jointly to Ernst Ruska (for his work on the
electron microscope) and to Gerd Binnig and Heinrich Rohrer (for the scanning
tunnelling microscope).
1992 – Green fluorescent protein (GFP) cloned
Douglas Prasher reports the cloning of GFP. This opens the way to widespread use of
GFP and its derivatives as labels for fluorescence microscopy (particularly confocal
laser scanning fluorescence microscopy).
1993–1996 – Super-resolution microscopy
Stefan Hell pioneers a new optical microscope technology that allows the capture of
images with a higher resolution than was previously thought possible. This results in a
wide array of high-resolution optical methodologies, collectively termed super-resolution
microscopy.
2010 – Atoms of a virus seen
Researchers at UCLA use a cryoelectron microscope to see the atoms of a virus.
2014 – Chemistry Nobel prize for super microscopes
Nobel Prize in Chemistry awarded to Eric Betzig, Stefan Hell and William Moerner for
the development of super-resolved fluorescence microscopy which allows microscopes
to now ‘see’ matter smaller than 0.2 micrometers.

4. IMPORTANCE AND USES
Microscopes are used in viewing the specimens that are relatively very small in size,
they are used to view the cellular structures of organs, germs, and bacteria, they play a
very important role in the laboratory for the tissues and organisms which are too small
to be seen clearly with the naked eye.
TYPES OF MICROSCOPES AND THEIR USES
5 Different Types of Microscopes:
1. Stereo Microscope
2. Compound Microscope
3. Inverted Microscope
4. Metallurgical Microscope
5. Polarizing Microscope
Stereo Microscopes
Are used to look at a variety of samples that you would be able to hold in your hand. A
stereo microscope provides a 3D image or "stereo" image and typically will provide
magnification between 10x - 40x. The stereo microscope is used in manufacturing, quality
control, coin collecting, science, for high school dissection projects, and botany. A stereo
microscope typically provides both transmitted and reflected illumination and can be used
to view a sample that will not allow light to pass through it.
Compound Microscopes
A compound microscope may also be referred to as a biological microscope.
Compound microscopes are used in laboratories, schools, wastewater treatment plants,
veterinary offices, and for histology and pathology. The samples viewed under a
compound microscope must be prepared on a microscope slide using a cover slip to
flatten the sample. Students will often view prepared slides under the microscope to
save time by eliminating the slide preparation process.
Inverted Microscopes
Inverted microscopes are available as biological inverted microscopes or metallurgical
inverted microscopes. Biological inverted microscopes provide magnification of 40x, 100x
and sometimes 200x and 400x. These biological inverted microscopes are used to view
living samples that are in a petri dish. An inverted microscope allows the user to place the
petri dish on a flat stage, with the objective lenses housed beneath the stage. Inverted
microscopes are used for in-vitro fertilization, live cell imaging, developmental biology,
cell biology, neuroscience, and microbiology. Inverted microscopes are often used in
research to analyze and study tissues and cells, and in particular living cells.

5. Metallurgical Microscopes
Are high power microscopes designed to view samples that do not allow light to pass
through them. Reflected light shines down through the objective lenses providing
magnification of 50x, 100x, 200x, and sometimes 500x. Metallurgical microscopes are
utilized to examine micron level cracks in metals, very thin layers of coatings such as
paint, and grain sizing.
Polarizing Microscopes
Polarizing microscopes use polarized light along with transmitted and, or reflected
illumination to examine chemicals, rocks, and minerals. Polarizing microscopes are
utilized by geologists, petrologists, chemists, and the pharmaceutical industry on a daily
basis. All polarizing microscopes have both a polarizer and an analyzer. The polarizer will
only allow certain light waves to pass through it. The analyzer determines the amount of
light and direction of light that will illuminate the sample. The polarizer basically focuses
different wavelengths of light onto a single plane. This function makes the microscope
perfect for viewing birefringent materials.
PARTS AND FUNCTIONS
1. Head – This is also known as the body; it carries the optical parts in the upper
part of the microscope.
2. Base – It acts as microscopes support. It also carriers the microscopic
illuminators.
3. Arms – This is the part connecting the base and to the head and the eyepiece
tube to the base of the microscope. It gives support to the head of the
microscope and it also used when carrying the microscope. Some high-quality
microscopes have an articulated arm with more than one joint allowing more
movement of the microscopic head for better viewing.
4. Eyepiece – also known as the ocular. this is the part used to look through the
microscope. It’s found at the top of the microscope. Its standard magnification
is 10x with an optional eyepiece having magnifications from 5X – 30X.
5. Eyepiece tube – it’s the eyepiece holder. It carries the eyepiece just above the
objective lens. In some microscopes such as the binoculars, the eyepiece tube
is flexible and can be rotated for maximum visualization, for variance in
distance. For monocular microscopes, they are none flexible.
6. Objective lenses – These are the major lenses used for specimen
visualization. They have a magnification power of 40x-100X. There are about
1- 4 objective lenses placed on one microscope, in that some are rare facing
and others face forward. Each lens has its own magnification power.
7. Nose piece – also known as the revolving turret. It holds the objective lenses.
It is movable hence its cal revolve the objective lenses depending on the
magnification power of the lens.

6. 8. The Adjustment knobs – These are knobs that are used to focus the
microscope. There are two types of adjustment knobs i.e. fine adjustment knobs
and the coarse adjustment knobs.
9. Stage – This is the section on which the specimen is placed for viewing. They
have stage clips hold the specimen slides in place. The most common stage is
a mechanical stage, which allows the control of the slides by moving the slides
using the mechanical knobs on the stage instead of moving it manually.
10.Aperture – This is a hole on the microscope stage, through which the
transmitted light from the source reaches the stage.
11.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.
12.Condenser – These are lenses that are used to collect and focus light from the
illuminator into the specimen. They are found under the stage next to the
diaphragm of the microscope. They play a major role in ensuring clear sharp
images are produced with a high magnification of 400X and above. The higher
the magnification of the condenser, the more the image clarity. More
sophisticated microscopes come with an Abbe condenser that has a high
magnification of about 1000X.
13.Diaphragm – it’s also known as the iris. It’s found under the stage of the
microscope and its primary role is to control the amount of light that reaches the
specimen. It’s an adjustable apparatus, hence controlling the light intensity and
the size of the beam of light that gets to the specimen. For high-quality
microscopes, the diaphragm comes attached with an Abbe condenser and
combined they are able to control the light focus and light intensity that reaches
the specimen.
14.Condenser focus knob – this is a knob that moves the condenser up or down
thus controlling the focus of light on the specimen.
15.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.
16.The rack stops – It controls how far the stages should go preventing the
objective lens from getting too close to the specimen slide which may damage
the specimen. It is responsible for preventing the specimen slide from coming
too far up and hit the objective lens.

7. HOW TO USE
1. Turn the revolving turret (2) so that the lowest power objective lens (eg. 4x)
is clicked into position.
2. Place the microscope slide on the stage (6) and fasten it with the stage clips.
3. Look at the objective lens (3) and the stage from the side and turn the focus
knob (4) so the stage moves upward. Move it up as far as it will go without
letting the objective touch the coverslip.
4. Look through the eyepiece (1) and move the focus knob until the image
comes into focus.
5. Adjust the condenser (7) and light intensity for the greatest amount of light.
6. Move the microscope slide around until the sample is in the centre of the
field of view (what you see).
7. Use the focus knob (4) to place the sample into focus and readjust the
condenser (7) and light intensity for the clearest image (with low power
objectives you might need to reduce the light intensity or shut the
condenser).
8. When you have a clear image of your sample with the lowest power
objective, you can change to the next objective lenses. You might need to
readjust the sample into focus and/or readjust the condenser and light
intensity. If you cannot focus on your specimen, repeat steps 3 through 5
with the higher power objective lens in place. Do not let the objective lens
touch the slide!
9. When finished, lower the stage, click the low power lens into position and
remove the slide.

8. HOW TO TAKE CARE
Tip 1: Handle with care
Most microscope problems occur as a result of improper handling. When carrying your
microscope, hold it by the base and the metal support arm. Do not pick it up by the
stage, as this can cause misalignment. When transporting it, use a microscope bag.
Tip 2: Keep lenses clear of slides
When using your microscope and adjusting the focus you will need to lower the
objective lens down as far as it will go. However, you should never allow the lens to
touch the slide you are looking at. Dirty lenses can be difficult to clean.
Tip3: Clean after using immersion oil
If using immersion oil, always ensure the objectives are cleaned immediately after use.
Objective, eyepieces and condenser may be removed for cleaning. Use only lens paper
and lens cleaner. Do not use solvents.
Tip 4: Cover when not in use
All microscopes are sold with dust covers. Always keep your microscope covered when
not in use even if the microscope is stored in a cabinet. Eye tubes also need to be kept
free of dust so do not store a microscope without the eyepieces. If the microscope
eyepieces must be removed, cover the tubes with caps or a plastic bag with a rubber
band around the eye tube.
Tip 5: Look after the bulb
After using the microscope, turn off the illuminator and wait for it to cool for several
minutes before putting it away. By allowing the bulb to cool you will extend its life. When
turning the microscope on and off, use the switch not the power point. Do not switch the
microscope on while using full light intensity. Never touch the bulb with your fingers as
the body oils can burn into the bulb and reduce its life. Use a tissue. Keep a store of
replacement bulbs and always use the correct bulb.
Tip 6: Store in a clean, dry place
Make sure you do not store your microscope in an area that has corrosive chemical
fumes that can destroy lenses or metal parts or beside solutions that may leak. Salt air
and pervasive damp can also cause damage over time. Make sure your cabinet is
ventilated.
Tip 7: Only use special lens paper or wipes for cleaning the lenses

9. Microscope lenses can easily be scratched and should be treated with great care. Use
an aspirator to remove dust. Sticky residue can be removed with lens paper moistened
with distilled water or lens cleaning solution and rubbed gently using a circular motion.
Never use sharp instruments or anything abrasive on the microscope lenses.
Tip 8: Keep your User's Manual and wrenches in a safe place
Each microscope should come with a user's manual and specialist wrenches as
required. Always consult the User's Manual before making any adjustments to your
microscope and use the wrenches provided. Never over-tighten or use force when
performing any maintenance on your microscope, or use inappropriate tools. This can
damage the parts.
Tip 9: Perform an annual maintenance check
On an annual basis moving parts on the microscope should be cleaned and lubricated.
Clean grease and dirt from sliding surfaces using a clean cloth. Apply a very thin layer
of lithium-based grease to the sliding surfaces. Do not grease the teeth of the rack and
pinion gears. Inspect the power cords and plugs for safety and stock up on a supply of
replacement bulbs.
Tip 10: Have your microscope serviced professionally
A rule of thumb for frequency of servicing is every 200 hours of use or every 3 years,
whichever comes first.