The document defines various types of microscopes and microscopy terms. It describes light microscopes like brightfield, phase contrast, and fluorescence microscopes which use lenses and visible light to magnify small specimens. Electron microscopes like transmission electron microscopes and scanning electron microscopes are also covered, which use electron beams instead of light to achieve higher magnifications. Key microscopy terms defined include magnification, resolution, numerical aperture, refractive index, and aberration. Specific uses and working principles of each microscope type are provided.

1. MICROSCOPE
It is a laboratory instrument used to examine objects that
are too small to be seen by the naked eye.
MICROSCOPY
It is the science of investigating small objects
and structures using a microscope.
Derived from Greek words “mikrós” meaning “small”
and “skópéō” meaning “look at”.

2. MICROSCOPY TERMS
MAGNIFICATION
It is the process of producing an enlarged
image of a specimen by using a lens system.
MAGNIFYING POWER
Magnifying power is how much larger a given lens can make an image appear.
It can be mathematically defined as;
M=1+ D/F
where,
M = magnifying power
D = least distance of distinct vision
F = Focal length of a convex lens

3. REFRACTIVE INDEX
It is the measure of bending of a light ray when passing from one medium to another.
Mathematically it can be defined as;
n = c/v
where,
n = refractive index
c = speed of light in vacuum
v = velocity of light in a medium
RESOLUTION
It is the ability of a microscope to distinguish details on a specimen.
Mathematically it is given as;
r = ⋋/2NA
where,
r = resolution
⋋ = imaging wavelength
NA = numerical aperture

4. The numerical aperture of a microscope objective is the measure of its ability to
gather light and to resolve fine specimen detail while working at a fixed object distance.
NUMERICAL APERATURE
NA = n sin θ
where,
n=Refractive index of the medium
θ is half the angular aperture
Deviation of light rays by lenses or curved mirrors which causes the images to be blurred.
ABERRATION

5. TYPES OF MICROSCOPE
ELECTRON MICROSCOPE
LIGHT MICROSCOPE
Bright field Light
Microscope
Phase Contrast Light
Microscope
Fluorescence Light
Microscope
Transmission electron
microscope
Scanning electron
microscope

6. Principle of a light microscope (optical microscope)
When a ray of light passes through one medium into another, the ray bends at
the interface causing refraction.
LIGHT MICROSCOPE
It uses visible light and a system of lenses to generate magnified images of
Small objects.
The maximum magnification power of optical microscopes is typically limited
To around 1000x .

7. BRIGHTFIELD MICROSCOPE
It is an optical microscope that uses light rays to produce a dark image against a bright
background.
The objectives have a magnification power of 40x-1000x depending on the type of
brightfield microscope while the eyepiece lens has a standard magnification
power of 10x.
USES
Used to visualize and study the animal cells.
Used to visualize and study plant cells.
Used to visualize and study the morphologies of bacterial cells.
Used to identify parasitic protozoans such as Paramecium.

9. PHASE CONTRAST MICROSCOPE
Phase-contrast microscopy is an optical microscopy technique that converts
phase shifts in the light passing through a transparent specimen to brightness
changes in the image
To produce high-contrast images of transparent specimens, such as
living cells (usually in culture)
microorganisms
thin tissue slices
lithographic patterns
fibers
latex dispersions
glass fragments
subcellular particles (including nuclei and other organelles).

11. DARKFIELD MICROSCOPE
USES
Viewing blood cells
Viewing bacteria
Viewing different types of algae
Viewing hairline metal fractures
Viewing diamonds and other precious stones Viewing shrimp or other invertebrates
Darkfield illumination is a technique in optical microscopy that eliminates scattered
light from the sample image.
This yields an image with a dark background around the specimen, and is essentially
the complete opposite of the brightfield illumination technique

13. FLUORESCENCE MICROSCOPE
A fluorescence microscope is an optical microscope that uses fluorescence and
phosphorescence instead of, or in addition to, reflection and absorption to study the
properties of organic or inorganic substances.
The “fluorescence microscope” refers to any microscope that uses fluorescence to
generate an image
•Observing the structure of a cell
•Observing DNA and RNA within a cell
•Creating an image of a single
molecule
•Studying cell populations
USES

15. ELECTRON MICROSCOPE
It uses a beam of accelerated electron as a source of illumination.
It use shaped magnetic fields to form electron optical lens system that are
analogous to the glass lenses of a optical light microscope.
They are used to investigate the ultrastructure of a wide range of biological and
Inorganic specimens including microorganisms, cells, large molecules and crystals.
Modern electron microscopes produce electron micrographs using specialized
Digital cameras and frame grabbers to capture images.

16. TRANSMISSION ELECTRON MICROSCOPE(TEM)
It uses a high voltage electron beam to illuminate the specimen and create an image.

17. SCANNING ELECTRON MICROSCOPE(SEM)
It is a type of electron microscope that produces images of a sample by scanning
The surface with a focused beam of electrons.

18. Bright field
Phase contrast
Dark field
Fluorescence TEM
SEM
BLOOD CELLS