This document discusses light microscopes. It begins by defining a microscope as an instrument used to view objects too small to see with the naked eye. It then describes the basic components and workings of light microscopes, including lenses that magnify objects, different types like brightfield and phase contrast, and applications in biology and medicine like pathology. Phase contrast microscopy is explained in more detail, noting how it uses interference of light waves passing through a specimen to visualize differences in brightness of structures. In closing, the document outlines several uses of light microscopes across various fields.

1. LIGHT MICROSCOPE
Presented by :- Prajapati Jinal V .
CBO :- 406
M.Sc Sem :- 2
Department of life sciences ,
H.N.G.U., Patan

2. CONTENT
• What is Microscope ?
• Light Microscope
Introduction
Principle
Types of light microscope
Application of light microscope

3. What is Microscope ?
• A microscope is an instrument used to see object that are too small
to be seen by the naked eye . Microscopy is the science of
investigating small object and structures using such an instrument .
• There are two type of the microscope :
1. Light Microscope
2. Electron Microscope

4. Light Microscope
 Introduction :-
• In 1590 F.H. Janssen & Zacharias Jansen constructed the first simple
light microscope .
• When molecular detail is not required ,the light microscope is an
ideal, and hence essential, instrument for a biologist .
• The simplest form of light microscope consists of a single glass lens
in combination .
• All modern light microscope are made up of more than one glass
lens in combination .

5.  Principle :-
• The light microscope operates on the principle that light energy will
pass through and around a thin object , such as a microorganism
and with the aid of lenses , form a magnified impression on the
visual sensory layer of the eye .
• The main components of the compound light microscope include a
light source that is Focussed at the specimen by a condenser lens .
• The source of light is usually the Sun or ambient indoor light .

6.  How does light microscopy work ?
• Light microscope are compound microscope , which means they
contain at least two lenses .
• Lenses are curved pieces of glass or plastic that bend rays of light
and can magnify objects, making them appear bigger than they
actually are .
• Light microscope shown here magnifies an object in two stages .
• Light from the mirror is reflected up through the specimen, or object
to be viewed, into the powerful objective lens, which produce the
first magnification .

7. • The image produced by the objective lens is than magnified again by
the eyepiece lens, which act as a simple magnifying glass .
• The magnified image can be seen by looking into the eyepiece lens.
• Important factor in light microscopy include :
1. Magnification
2. Resolution
3. Contrast

9.  Types of Light microscope :-
1. Bright - field Microscopy
2. Dark – field Microscopy
3. Phase contrast Microscopy
4. Fluorescence Microscopy
 Phase contrast Microscopy :-
• Phase contrast microscopy first described in 1934 by Dutch physicist
Frits Zemike .
• A Phase contrast microscope makes it possible by utilizing two
characteristics of light, diffraction and interference, to visualize
specimens based on brightness differences .

10.  Principle :-
• The Principle of Phase contrast microscopy is based on the wave
nature of light rays and the fact that light rays can be in phase or out
of phase .
• In a Phase contrast microscope, one set of light rays comes directly
from the light sources .
• The other set comes from light that is reflected or diffracted from a
particular structure in the specimen .

11.  How does Phase contrast microscope work ?
• Light that does not interact with the specimen is collected by the
objective, passes through the Phase plate ring , and is retarded
exactly ¼ wavelength .
• The Phase shifted is not detectable by the eye so the resulting image
on the image plane in the microscope appears as a normal bright
background .
• Light passing through one material & into another material of
slightly different refractive index or thickness will undergo a charge
in phase .this charge in are translated into variations in brightness of
the structures .

14. Application of Light Microscope
• The light microscope can be used to provide information about the
activity of cells and to look at very small structures such as
nanostructures .
• Different adaptations can help to enhance images , such as phase
contrast microscopy , which provides contrast between cells and the
solution they are in .
• Light microscope is a great use in pathology labs so as to identify
diseases.
• Light microscopy can be used to explore the time and space related
dynamics of molecules .

15. • Light microscopy has a number of applications in different sectors
including in gemmology , metallurgy and chemistry .
• In terms of biology , it is one of the least invasive techniques for
looking at living cells .
• Phase contrast microscope is most useful for examining intracellular
components of living cells at relatively high resolution .
• Students in schools and colleges are benefited by the use of a light
microscope for conducting their academic experiments .
• It is widely used in microbiology and tissue culture research to
detect bacteria, cellular organelles or for testing cell and organelle
preparations for lysis .

16. REFERENCES
• Principles and Techniques of Biochemistry and Molecular Biology :
by:- Keith Wilson
John Walker
 https://en.m.Wikipedia.org
https://www.dkfindout.com

17. THANK YOU