Light microscope

imp.part of microbiology laboratory for detecting the microorganism.

1. LIGHT MICROSCOPE BY-: Abhishek Singh Medical Microbiology

2. INTRODUCTION and history The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples . In 1590 F.H Janssen & Z.Janssen constructed the first simple compound light microscope. In 1665 Robert Hooke developed a first laboratory compound microscope. Later, Kepler and galileo developed a modern classroom microscope. In 1672 Leeuwenhoek developed a first simple microscope with a magnification of 200x -300x. He is called as Father of microscopy. The term microscope was coined by Faber in 1623.

3. Light MICROSCOPE

4. Parts of light microscope Illuminator - This is the light source located below the specimen . Condenser - Focuses the ray of light through the specimen. Stage - The fixed stage is a horizontal platform that holds the specimen. Objective - The lens that is directly above the stage . Nosepiece - The portion of the body that holds the objectives over the stage. Iris diaphragm - Regulates the amount of light into the condenser. Base – Base supports the microscope which is horseshoe shaped. Coarse focusing knob - Used to make relatively wide focusing adjustments to the microscope. Fine focusing knob - Used to make relatively small adjustments to the microscope. Ocular eyepiece - Lens on the top of the body tube. It has a magnification of 10× normal vision.

5. Principle of light microscope Light from an incandescent source is aimed toward a lens beneath the stage called the condenser through the specimen ,through an objective lens and to the eye through a second magnifying lens the ocular or eyepiece. The condenser is used to focus light on the specimen through an opening in the stage. After passing through the specimen the light is displayed to the eye with an apparent field that is much longer then the area of illumination .

6. Light Microscope Resolution Ability of a lens to separate or distinguish small objects that are close together Wavelength of light used is major factor in resolution Increase in size (greater magnification) without the ability to distinguish structural details(greater resolution) is not beneficial shorter wavelength  greater resolution

7. limits of resolution The resolving power of human eye is 0.25 mm The light microscope can separate dots that are 0.25µm apart. The electron microscope can separate dots that are 0.5nm apart.

8. Numerical aperture The numerical aperture of a lens is the ratio of the diameter of the lens to its focal length. NA of a lens is an index of the resolving power. NA can be decreased by decreasing the amount of light that passes through a lens. Diameter of the lens

9. magnification of light microscope It is the ratio of the size of an object seen under microscope to the actual size observed with unaided eye. The total magnification of microscope is calculated by multiplying the magnifying power of the objective lens by that of eye piece

10. The Concept of Magnification Magnification of the Microscope M Microscope = M Objective X M Eyepiece X M Intermediate Factor M = Magnification Example: Objective = 60 x Eyepiece = 10 x Intermediate Factor = 1 x Overall M = 600 x

11. PROPERTY LOW POWER HIGH POWER OIL IMMERSION Magnification of objective 10x 40-45x 90-100x Magnification of eyepiece 10x 10x 10x Total magnification 100x 450 – 450x 900 – 1000x

12. The effects of immersion oil on resolution

13. Images of light microscope Baccili and cocci under light microscope

14. Care of the microscope Hold a microscope firmly by the stand, only. Never grab it by the eyepiece holder. Hold the microscope by arm and stage. Since bulbs are expensive, and have a limited life, turn the illuminator off when you are done. Always make sure the stage and lenses are clean before putting away the microscope. NEVER use a paper towel or any material other than good quality lens tissue or a cotton swab (must be 100% natural cotton) to clean an optical surface. Use an appropriate lens cleaner or distilled water to help remove dried material. Organic solvents may separate or damage the lens elements or coatings. Cover the instrument with a dust jacket when not in use. Focus smoothly; don't try to speed through the focusing process or force anything.