Introduction to microscopy

compound microscope, phase contrast microscope etc

1. INTRODUCTION TO MICROSCOPY Mr.R.R.Patil Dr.Shivajirao Kadam College of Pharmacy, Kasabe digraj, Sangli

2. INTRODUCTION Defin : It is an optical instrument consisting of lens or combination of lenses for making enlarge or magnified image of minute object. The science dealing with all aspects of a microscope is called microscopy.

3. Classification of microscope Depending on number of lenses i . Single microscope ii. Compound microscope Depending on number of eyepiece i . Monocular microscope ii. Binocular microscope Depending on source i . Light or optical microscope ii. Electron microscope

4. Compound Microscope In compound microscope three essential systems included… Support system: base, pillar, stage & body tube. Illumination system: light source or mirror, iris diaphragm & condenser. Magnification system: objective & eyepiece.

5. IMAGE OF COMPOUND MICROSCOPE

6. IMAGE OF BINOCULAR MICROSCOPE

7. IMPORTANT TERMS OF MICROSCOPY Magnification Working distance Resolving power Numerical aperture

8. Magnification The degree of enlargement is called magnification or magnifying power of the instrument. The magnification is effected in two stages.. i . By the objective lens ii. By the eye-piece lens

9. Magnification of the microscope can be calculated by multiplying the magnification power of the objective by that of eye-piece. The magnifying ability is denoted by ‘X’ symbol.

10. Working distance Defined as the distance between the front lens of the objective & the object on the slide. Working distance easily determined by noting the number of complete turns of the microscope to raise the object from the surface of slide.

11. Resolving power It is defined as the ability to distinctly separate two small elements in the structure of an object that are a short distance apart. Resolving power is expressed quantitatively as the microscope’s limit of resolution (LR).

12. Numerical aperture(NA) It is defined as the simply diameter of the lens to its focal length. It is expressed mathematically as.. NA = n sin ø Where, n = refractive index of the medium between object & objective.

13. Phase- Contrast Microscope Phase contrast microscope is an optical- microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase contrast microscope discovered by Fritz Zernik . In 1953 he won the N obel prize in physics.

14. Image of Phase-contrast microscope

15. Construction & Working In phase contrast microscope has a special type of diaphragm consisting of an annual stop. The annular stop allows only a hollow cone of light rays to pass through the condenser. Ii is also consist of phase plate. Phase plate has a special ring coated with a material that can retard the direct rays or undiffracted rays & are unaltered in amplitude & phase. Then those rays are bend & slowed down due to difference intensity of medium are called diffracted rays.

16. The condenser of a phase-contrast microscope has an annular stop , an opaque disk with a thin transparent ring, which produces a hollow cone of light . As this cone passes through a cell, some light rays are bent due to variations in density and refractive index within the specimen and are retarded by about 1/4 wavelength. The diffracted light is focused to form an image of the object. Undiffracted light rays strike a phase ring in the phase plate, a special optical disk located in the objective, while the diffracted rays miss the ring and pass through the rest of the plate.

17. Finally all rays means undiffracted & diffracted rays come together by an eyepiece lens. This type of microscopy is called dark-phase-contrast microscopy . Phase-contrast microscopy is especially useful for studying microbial motility, determining the shape of living cells , and detecting bacterial components.

18. THANK YOU