MICROSCOPY
FIS201G2
Properties of Light
When a ray of light strikes an object. Three things can happen. They
are
Reflection- if the ray bounce back
Transmission- If it is passes through it.
Absorption- if it transfers through the objects, some or all of its
energy absorb by that
Diffraction of Light
 When ray of light pass through a small opening/ pass by edge of an
opaque objects, light ray bend.
 This kind of bending is called as Diffraction. Diffraction occur
because of the wave nature of light
Refraction of Light
 Refraction also bending rays of light but by different mechanism. It
occurs when a ray of light meets an object of a different density at
an angle.
MICROSCOPE
Microscope
 The word “microscope” comes from the Latin “microscopium,”
which is derived from the Greek words “mikros,” meaning “small,”
and “skopein,” meaning “to look at.”
 Microscope, instrument that produces enlarged images of small
objects, allowing the observer an exceedingly close view of minute
structures at a scale convenient for examination and analysis.
 Naked eye helps to view the objects down to 1 mm, light and
electron microscopes are indeed needed to study the objects in the
range 1 mm - 300 nm and 300 nm - 0.2 nm, respectively.
History of Microscopy
• There is no one person who invented the microscope as several
different inventors experimented with theories and ideas and
developed different parts of the concept as they evolved to what is
today’s microscopes.
• About 1590 two Dutch spectacle makers, Zaccharias Janssen and
his son Hans, experimented with a crude concept of a microscope
that enlarged objects 10x to 30x or so.
• In 1609, Galileo (an Italian) improved on the principle of lenses
and added a focusing device to improve somewhat upon what the
Janssen’s had done.
History of Microscopy
History of Microscopy
• Early 1670s. A Dutchman, Anton van Leeuwenhoek, is considered
the father of microscopes because of the advances he made in
microscope design and use.
• He worked as an apprentice in a dry goods store where
magnifying lenses were used to count the threads in cloth.
• Anton was inspired by these glasses and he taught himself new
methods for grinding and polishing small lenses which magnified
up to 270x. This led to the first practical microscopes.
• In 1674, Anton was the first to see and describe bacteria, yeast,
plants, and life in a drop of water.
History of Microscopy
In 1733 the amateur English optician Chester
Moor Hall found by trial and error that a
combination of a convex crown-glass lens and a
concave flintglass lens could help to correct
chromatic aberration in a telescope.
In 1774 Benjamin Martin of London produced a
pioneering set of colour-corrected lenses for a
microscope
History of Microscopy
In the early 1930’s the first electron beam microscopes were
developed which were a breakthrough in technology as they
increased the magnification from about 1000x or so up to
250,000x or more.
These microscopes use electrons rather than light to examine
objects.
History of Microscopy
Modern Microscopes: In 1900's, iron based
structures were used to develop a microscope
due to its cheaper cost; Only one eyepiece
(monocular); Outside light source; reflected
onto mirror; Very functional; Still used today.
History of Microscopy
Later on, Fancy type microscopes as shown in
Figure were developed (1998's). This provided
• Better images
• Large magnification
• Better lighting
• Easier to use
How does it work?
A microscope works very much like a
telescope.
A telescope must gather light from a dim,
far away object as depicted in below
Figure
How does it work?
So, it needs a large objective lens
to gather as much light as
possible and a long body to bring
the image into focus.
On the other hand, Unlike a
telescope, a microscope must
gather light from a tiny specimen
that is located close-by as shown
in Figure
How does it work?
• So the microscope does NOT need a
large objective lens.
• Instead, the objective lens of a
microscope is small.
• Then the image is again magnified by a
second lens, called an eyepiece, as it is
brought to your eye.
Microscopes in Medicine
Pasteur’s germ theory revolutionized the process of identifying,
treating and preventing infectious diseases.
Today, hospital laboratories use microscopes to identify which
microbe is causing an infection so physicians can prescribe the proper
antibiotic.
They are also used to diagnose cancer and other diseases.
Investigating With Microscopes
• Many types of scientists, seeking to understand the natural and
physical world better, use microscope in their work.
• Forensic scientists examine blood, dust, fibers and other trace
materials at a crime scene to help prosecute criminals.
• Environmental scientists examine soil and water samples, while
geneticists observe chromosomes for defects. In engineering,
material scientists use microscopes to inspect the components of
structures such as buildings, bridges and dams to ensure that they
are safe.
Microscopes in Education
• In the classroom, microscopes are used to teach students about
the structure of things too small to be seen with the human eye
alone.
• The individual cells of plants, animals, bacteria and yeast can all
be seen using a compound microscope.