Coverage for Midterm Exam Lab PDF

THE MICROSCOPE Is a combina on of two words: micro, meaning “small,” and scope meaning “view”. This instrument is designed to produced magnified visual or photographic images of objects too small to be seen by the naked eye. 2 basic kinds of microscope: SIMPLE...

THE MICROSCOPE Is a combina on of two words: micro, meaning “small,” and scope meaning “view”. This instrument is designed to produced magnified visual or photographic images of objects too small to be seen by the naked eye. 2 basic kinds of microscope: SIMPLE Used by Anton van Leeuwenhoek were described as “simple” since they only had one lens. They produced an enlarged, upright image of the specimen Only magnify an object more or less 200 mes its original size. COMPOUND Invented by Janssen brothers  They introduced a second lens system Today, modern compound light microscope, under op mal condi on, can magnify a specimen from 1000 to 2000 mes its original size Kinds of microscope LIGHT MICROSCOPE- the term light refers to the process by which light transmits the image to the eye. Light microscopes are of two basic types Compound microscope- is an op mal instrument with a two-lens system- the objec ves and the eyepiece or ocular. It requires that the material being examined be sliced thinly enough to for light to pass through, It can magnify the specimen up to 1,500 mes Dissec ng microscope- permits the viewing of opaque objects. Most dissec ng microscope can magnify up to 30 mes. Electron microscope- a microscope that can magnify very small details with a high resolu ons. Its high magnifying capacity is due to the use of electrons rather than light to sca er off material, magnifying at levels of more or less 500,000 mes the original size. Transmission electron microscope (TEM) – uses a high-voltage electron beam emi ed by a cathode and formed by magne c lenses. Using a very thin sec on of the specimen, this electron beam can carry and transmit informa on about the internal structure of the sample. It can magnify the specimen up to more or less 200 000 mes its original size Scanning electron microscope (SEM)- makes use of beam transmission. It produces image by detec ng secondary electrons, which are emi ed from the surface due to excita on by the primary electron beam. The surface of the specimen is bombarded with electron to allow scien st to see a three-dimensional image of the specimen’s surface. It can magnify from 3,000 to 10 000 mes its original size Scanning transmission electron microscope (STEM)- a specific type of TEM in which the electrons s ll pass through the specimen, but as in SEM, the sample is scanned through a beam of electrons Scanning tunneling microscope (STM) – the newest machine that can reveal individual atoms only three Angstrom across. It works on the principle of electron tunneling, which refers to the tendency of electron to jump between the p of a fine metal needle and the surface to be studied. It produces a three-dimensional image by scanning the surface of the sample with a beam of electrons. COMPOUND MICROSCOPE  Is an op cal instrument with a two-lens system- objec ve and the eyepiece, or ocular. monocular (with only one eyepiece/ocular) binocular (with two eyepiece- one for each eye of the observer)   3 main parts of microscope Mechanical Magnifying Illumina ng COMPOUND MICROSCOPE 1. Mechanical Parts a) Base- usually U- or V- shaped. This is where the microscope firmly rests. b) Arm- connects the base and the body tube together. It serves as a handle for carrying the microscope. c) Stage- the pla orm that holds/supports the slide containing the specimen. It has an opening at the center that allows the light to pass from below into the specimen for study d) Pillar- the support or post of the base where the arm is a ached e) Stage clips/caliper- hold the specimen firmly on the stage. f) Substage- found below the stage; it holds the Abbe condenser above and the iris diaphragm below. g) Body tube- cylinder that a aches the draw tube into the microscope and acts as the passageway of the light from the objec ve to the eyepiece h) Coarse adjustment- upper, larger knobs used to bring an object into focus only while it is being viewed under the low-power objec ve (LPO) i) Fine adjustment – lower, smaller knobs for the slow movement of the body tube when focusing under the high-power objec ve (HPO) and other high-powered lenses. j) Revolving nosepiece- carries the objec ves. Turned to select the appropriate objec ve. The lenses must be “clicked” in the place for the field to be visible k) Draw tube- the smaller cylinder a ached to the upper part of the body tube that holds the ocular l) Eyepiece or ocular – detachable cylinder located at the upper end of the tube. It may have a line inside that serves as a pointer and rotates as the ocular is rotated. m) Objec ves – usually, an ordinary laboratory microscope has two or three objec ves a ached to the revolving nosepiece. These are the scanner, and the low- and high- power objec ves.  2. Magnifying parts Common values are 10x for the low power, 40x for the high power, and 100x for the oil immersion objec ve. a) Scanner objec ves – the shortest cylinder with a very large opening. It is provided with a large lens for a very low magnifica on and is used to observe a much wider field of the object. It is usually marked “5x”. b) Lower power objec ves – shorter cylinder with a large lens opening. It is used to observed the general outline and locate the various parts of the specimen. It is focused by using the coarse adjustment c) High power objec ve – longer cylinder with a small lens opening. It is equipped with lenses of high magnifying power and is used to study the detailed parts of the specimen. It is focused by using the fine adjustment course d) Oil immersion objec ve - longest cylinder with a very small lens opening. It is equipped with very small lenses for very high magnifica on and is used to study the details of specific parts of the specimen. A small drop of special oil is needed so that the light passing through it is uniformly distributed, or dispersed 3. Illumina ng parts a) Mirror/Illumina ng condenser – planar on one side and concave on the other. It is used to reflect light through the object and the lenses of the eyes. The concave side of the mirror is used for natural light, while that flat side is used for ar ficial light. It is held by the mirror rack. Cau on : never use direct sunlight, as it may damage the lenses of the microscope and also injure your eyes. b. Abbe Condenser – located on a substage held in place by a rack. It is used to condense or concentrate the light reflected from the mirror onto the object or specimen being examined. c. Diaphragm – It’s also known as the iris. It is found under the stage of the microscope, and its primary role is to control the amount of light that reaches the specimen. It’s an adjustable apparatus, hence controlling the light intensity and the size of the beam of light that gets to the specimen. COMPARISON BETWEEN MAGNIFICATION and RESOLUTION MAGNIFICATION  is the process of enlarging an object by using an op cal instrument or an increase in apparent size RESOLUTION  ability of an op cal instrument to produce images that are clearer, finer, and sharper in texture   measure of clarity  ability to show two objects as separate RULES FOR THE CARE OF THE MICROSCOPE: 1. In carrying the microscope, GRASP THE ARM WITH ONE HAND AND PLACE THE OTHER HAND UNDER THE BASE FOR SUPPORT 2. Never allow the objec ve to touch the cover glass or the liquid in which the object is mounted. 3. Never touch the objec ve or ocular lenses with your fingers or clothes. 4. Never change from lower to higher power objec ve without first checking that the body tube has been raised sufficiently to allow the high power objec ve to be slipped into place without injury to the objec ve or mounts. 5. Never clean the microscope lenses or stand with a cloth that has been used for removing a surplus/residue of alkali, acid, or another reagent from slides. 6. Note whether the front lens of the objec ve is clean before a emp ng to use it. If soiled, breathe on the lens and gently wipe with an old, clean, so handkerchief or lens paper. If the lens is soiled with balsam or some other s cky substance, moisten the handkerchief or lens paper with a drop of xylol. Take care to wipe it perfectly and dry it as soon as possible. 7. Do not let the objec ve remain long near corrosive liquids, such as strong solu ons of iodine, corrosive sublimate, or mineral acids. Never examine objects lying in such fluids without pu ng on a cover glass. 8. Never li the slide from the stage, but a er raising the objec ve, slide it off the stage without upward movement. 9. Never allow the stand (microscope without lenses) to be we ed with such substances as alcohol, soap, etc., which dissolve lacquer. 10. Keep the microscope covered when not in use.