Microscopy Lecture 2 PDF

Laboratory Lecture 2  Light Microscope Microscope is used to view objects or specimens that are too small to be seen with just the human eye. Microscopy is a technical field that involves the use of Microscopical components such as microscopes or microscope objectives to...

Laboratory Lecture 2  Light Microscope Microscope is used to view objects or specimens that are too small to be seen with just the human eye. Microscopy is a technical field that involves the use of Microscopical components such as microscopes or microscope objectives to obtain greater detail of examined samples. Definition-A microscope is a high precision optical instrument that uses a lens or a combination of lenses to produce highly magnified images of small specimens or objects especially when they are too small to be seen by the naked (unaided) eye. A light source is used (either by mirrors or lamps) to make it easier to see the subject matter.  TERMS AND DEFINITIONS Principle Microscopy is to get a magnified image, in which structures may be resolved which could not be resolved with the help of an unaided eye. Magnification 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. Types of light microscopes  Objective lenses One of the most important parts of a compound microscope, as they are the lenses closest to the specimen. Most compound microscopes have three or four (occasionally five) objectives usually of 4x, 10x, 40x, and 100x (oil immersion) which revolve on a nosepiece (turret) to give different magnifying powers. Total magnification: Ocular lens 10 X Objective lens  Total magnification Ocular lens 10x Objective lens ? Total= Ocular lens X Objective lens 4x= 10x= 40x= 100x=  Ocular Lens or Eye piece The eyepiece consists of a series of lenses mounted in a tube (barrel) at the upper end of the microscope. Its basic function is to look at the focused, magnified image projected by the objective lens and magnify that image a second time before your eye looks at the image of the specimen. The eyepieces are usually 10x but also come in 5x, 12.5x, 15x, and 20x. The “x” refers to the amount of magnification (power) that this lens adds as a multiplier to the magnification of the objective. The eyepoint is the location (or position) of the eye from the eyepiece which allows for the best possible viewing of the image.  Other parts Diopter Adjustment: Useful as a means to change focus on one eyepiece so as to correct for any difference in vision between your two eyes. Body tube (Head): The body tube connects the eyepiece to the objective lenses. Arm: The arm connects the body tube to the base of the microscope. Coarse adjustment: Brings the specimen into general focus. Fine adjustment: Fine tunes the focus and increases the detail of the specimen. Nosepiece: A rotating turret that houses the objective lenses. The viewer spins the nosepiece to select different objective lenses. Specimen or slide: The specimen is the object being examined. Most specimens are mounted on slides, flat rectangles of thin glass.  Stage: The flat platform where the slide is placed. Stage clips: Metal clips that hold the slide in place. Stage height adjustment (Stage Control): These knobs move the stage left and right or up and down. Aperture: The hole in the middle of the stage that allows light from the illuminator to reach the specimen. On/off switch: This switch on the base of the microscope turns the illuminator off and on. Illumination: The light source for a microscope. Illumination is the application of light onto an object or specimen in a microscope. Condenser: Gathers and focuses light from the illuminator onto the specimen being viewed. Base: The base supports the microscope and it’s where illuminator is located.