Light microscopy uses visible light and a system of lenses to magnify small samples. It has been used since the 17th century and remains a popular technique due to its simplicity. The basic components are a light source, lenses of varying magnification, and mechanical stages to position samples. There are three main types - brightfield microscopy uses transmitted light, phase contrast separates illuminated and scattered light, and darkfield blocks light entering directly to view transparent samples. Each technique has advantages for examining different types of unstained or living specimens.

1. JIWAJI UNIVERSITY
SUBMITTED BY :
MANISHA SINGHAI
M.Sc. MHG 4TH SEM
CENTRE FOR GENOMICS
TOPIC : LIGHT MICROSCOPY

2. CONTENTS
• INTRODUCTION
• COMPONENTS OF LIGHT MICROSCOPY
• PRINCIPLE AND FUNCTION
• TYPES OF LIGHT MICROSCOPY
• REFERENCES

3. INTRODUCTION
• Light microscope often referred to as the optical microscope .it is an type
of microscope which uses visible light and a system of lens to magnify
image of small samples.
• It is an oldest design of microscope and possibly designed in their present
compound forming in the 17th century
Bio science .com

4. • Historically light microscope where easy to develop and are popular
because they use visible light so that sample may be directly observed by
eye
• A light microscope work on a lot like a refracting telescope except that the
object is very close to objective lens .
• Light microscope may simple or compound

5. Components of light microscope
• There is a body tube with an ocular or eye piece mounted at its upper end
& objective lens of different magnifying power
• Arms hold the movable body tube in front & is fixed in the base
• There are two focusing knob one for coarse focusing & other for the fine
focusing
• Object stage is rigid platform with an aperture through which light rays
can pass
• Light sources a reflecting mirror is placed below the stage which reflect
sun light on objective
• Mechanical stage is equipped with scale which permit accurate mechanical
positioning of slide
• Lens system the compound microscope comprises three kind of lenses

6. • The condenser is located below the stage & above the mirror . It collected
and focus the light rays into the plane of objects that take no part in image
formation
• The objective this are mounted on revolving nose pieces. 10X ,40X, &
100X are magnification of objective lenses . It collect light rays from object
& from magnified real images.
• Ocular of eye piece at top of body tube . A monocular microscope consist
of one ocular ,while binocular microscope have two ocular of similar
magnification generally , ocular with 5x, 12.5x &15x lenses are available
the ocular magnifies the image formed by objective

7. Microscope international.com

8. Working principle
• Illumination light microscope with built in illumination use kohler or
kohler type illumination . In this type of illumination there are adjustable
collector lens in front of the source of light
• Image formation occurs in two stages the first is formed by the objective .
It is real , invert and magnified. The second is formed by ocular . It is
virtual inverted & more magnified
• Three principle is main for microscope
A. Magnification
B. Resolution
C. contrast
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9. Types of light microscope
 Bright field microscope
 Phase contrast microscope
 Dark field microscope

10. Bright field microscope
• Brightfield microscopy is the most elementary form of microscope
illumination techniques and is generally used with compound microscope
• The name “brightfield” is derived from the fact that the specimen is dark
and contrasted by the surrounding bright viewing field . Simple light
microscope sometimes referred to as brightfield microscopes.

11. Medical dictionary .com

12. Phase contrast microscope
• The basic principle to making phase changes visible in phase- contrast
microscopy is to separate the illuminating ( background light) from the
specimen – scattered light and to manipulate these differently .
• Ring shaped illuminating light that passes the condenser annulus is focused
on the specimen by the condenser . some of the illuminating light is
scattered by the specimen and form the background light
• When observing unstained biological specimen , the scattered light weak
and typically phase- shifted by -90 relative to background light . This leads
to foreground and background having nearly same intensity , resulting in
low image contrast

13. Microbes notes.com

14. Dark field microscope
• A dark field microscope is used to examine live microorganism that either
invisible in the ordinary light microscope , cant be stained by standard
methods , or are so distorted by staining that their characteristics then
cannot be identified
• Instead of normal condenser , dark field microscope uses a dark field
condenser that contain a opaque disc .
• Disc blocks light that would enter the lens directly , only the light is
reflected off the specimen would enter the objective lens .

15. Serc.carlton.edu

16. Advantages
• Brightfield microscope –it is very simple to use with fewer
adjustments needed to be made to view specimens
• Some specimens can be viewed without staining and optics used in the
brightfield technique don’t alter the color of specimen.
• Phase contrast microscope- unstained paraffin, resin & frozen
sections.
• Living cells and their behavior
• Cell organelles ,esp. mitochondria
• Capsules of microorganism

17. • Dark field microscopy- it allows researcher to identify various
different molecules in targeted specimen.
• a dark field microscope is ideal for viewing objects that are unstained,
transparent and absorbs little or no light
• It is more useful in examining external details, such as outlines , edges ,
grain boundaries and surface defects
• Use of this microscopy to study about marines organism such as algae and
plankton , insects, thin polymers and some ceramics .

18. REFERENCES
• The principle and practice of light microscopy( Cambridge university
press)
• Classification of microscope( JR BLUEFORD)