Microscopy Honors Biology Orders of Magnitude What would it look like to go from 10 million light years from Earth to an atom in an oak tree leaf in Tallahassee, Florida? Lets see.shall we? Honors Biology Vocabulary Honors Biology Magnification - making an image appear larger than its actual size. 2.Resolution - how clear an image is 3.Microscope - instrument for viewing objects too small to be seen by the naked eye. 4.Field of View - how much area you actually see when looking through the microscope 5.Depth of Field - the thickness of the specimen that is acceptably sharp at a given focus level Microscope History Honors Biology Zaccharias Janssen and son, Hans (1590): Lenses Galileo (1609): Magnifying tube Robert Hooke (1665): Compound microscope & cork Anton van Leeuwenhoek (1674): microscope powerful enough to see bacteria How do we see? Honors Biology Kinds of Microscopes 1.Dissecting Microscope 2. Optical (Light) Microscopes 3.Scanning Electron Microscope 4.Transmission Electron Microscope Dissecting Scope Light illuminated Image is 3-D Low magnification Used primarily during dissection for better views of specimen. Cannot view individual cells. Honors Biology Light (Optical) Microscopes Light passes through specimen Refractive lenses COMPOUND light microscopes use 2 lenses 2-Dimensional ~ size of a bacterium Usually magnifies 10x or 40x, 100x, and 400x But up to 1500x Can be used to study live cells Honors Biology Electron Microscopes Uses electrons to form an image of an object 100x light microscope i.e. viruses and bacteria Magnification: up to 200,000 x Can only be used on dead cells Honors Biology 2 Kinds of Electron Microscopes 1)Transmission Electron Microscope (TEM) Electron beam through thin section of specimen 2D image 2)Scanning Electron Microscope (SEM) Specimen - whole & plated in gold Electrons bounce off sample 3D Image Honors Biology What in the World? Honors Biology What in the World? Honors Biology What in the World? Honors Biology What in the World? Honors Biology What in the World? Honors Biology SEM Images Honors Biology SEM Images Honors Biology The Compound Light Microscope Eyepiece Lower-power objective Nosepiece Body tube Coarse adjustment Fine adjustment Stage Stage clips Diaphragm Light source Arm Base Honors Biology Using a Compound Light Microscope 1) Total magnification = Eye piece x objective lens Example: (10x) x (30x) = 300x Magnification Examples 2)Cover slips - No bubbles! 2)Focusing - Coarse 1st! Honors Biology Making a Wet Mount Slide Honors Biology Questions How do you place a cover slip on a slide? What objective do you start your viewing with? As you focus, what do you need to be sure to watch out for? Honors Biology