Dark field microscopy is a specialized technique that forms bright images against a dark background, primarily used to visualize transparent and semi-transparent objects not seen in bright-field microscopy. It employs a dark field microscope, which includes a special condenser and a dark field stop to illuminate samples effectively. The method is simple, inexpensive, and useful for studying certain microorganisms, although it has limitations in color range and light intensity.

1. DARK Field MICROSCOPY
-VAISHNAVI NIKTE

2. MICROSCOPE
It is optical instrument consists of a lens or a combination of lens which magnify minute objects
Types
- On the basis of lens
1. Simple Microscope.
2. Compound Microscope.
- On the basis of eyepiece
1. Monocular Microscope.
2. Binocular Microscope.
- On the basis of source
1. Optical Microscope.
2. Electron Microscope.

3. MICROSCOPY
Defination
Microscopy is a branch of science which deals with the study of all aspects related
to microscopy.
Microscopy
Optical Microscopy Electon Microscopy

4. Types of Microscopy
Optical Microscopy
1. Bright-field microscopy
2. Phase contract microscopy
3. Fluorescence microscopy
4. Dark-field microscopy
Electron Microscopy
1. Trasmission electron microscopy
2. Scanning electron microscopy

5. Dark field microscopy (Dark ground)
1. Dark field microscopy is the most specific and sensitive techique.
2. It forms a bright image aganist a dark backgournd Using dark feild microscope is
known as dark feild microscopy.
3. Mostly used to vIsualize the transparent and semi-transparent objects which are not
visible in bright-feild microscopy.
Principle
Visibility is dependent upon contract between object and its backgournd and can
improved by using a dark background.
For dark field microscopy Inverted Microscope is used.i.e Dark field microscope

6. Dark Field Microscope
Dark field microscope consists of-
1. Eyepiece.
2. Objective lens.
3. Stage.
4. Condenser lens(special condenser).
5. Dark field stop.(specially sized disc).

7.  Special condenser is newly added part in this microscope.(numerical aperature
Greater than 0.40.
 Mostly two types of special condenser are used.
1. Dry 100(NA 0.65).
2. Oil 100(NA 1.25).
 Dark field stop is used to blocks the light pass towards the condenser.
Numerical Aperature
Daimeter of lens to its focal length.

8. MECHANISM

9. Light pathway
1. Light enters the microscope for illumination of sample.
2. A special sized disc i.e Dark field stop blocks some light from the light
source,leaving an outer ring illumination.
3. Then,Condenser lens focous some light towards the sample.Most of the light is
directly transmitted ,while some is scattered from the sample.
4. After that scattered light enters the objective lens,whole trasmitted light simply
misses the lens and flows on the objective aperature.and is not collected due to
direct illumination block.
5. Only a scattered light goes on to produce the image and direct trasmitted light is
omitted.
6. This penomenon shows the bright image aganist a dark background.

10. ADVANTAGES & DISADVANTAGES
 Advantages:-
1. Simple to use.
2. Very effective to show details about trasparent semitrasparent water born singke
celled microorganism.
3. Inexpensive to setup.
 Disadvantages:-
1. Limited colors.
2. Low level of light.
3. Can’t study the internal features of microorganism.

11. Thank You!!