Basic Microscopy SC 912 L 14 4 Compare

Basic Microscopy SC. 912. L. 14. 4 - Compare and contrast structure and function of various types of microscopes. From the Virtual Microbiology Classroom on Science. Prof. Online. com Image: The Far Side by Gary Larson

Microscope History • Robert Hooke (1665) – Observed “cells” in cork • Anton van Leeuwenhoek (1674) – Father of Microscopy – Saw tiny living organisms in pond water.

Compound Light Microscope The “Compound” Part • Simple microscopes have single magnifying lens • Compound microscopes have two sets of lenses for magnification. • ocular lens = Lens closer to the eye • objective lens - Lenses closer to the object being viewed (Most light microscopes used in biology have three or four magnifying glass). (like a (magnifying power of 10 x). objective lenses). The “Light” Part • Bright-field light microscopes produce a dark image • Provide a 2 -D image. • Commonly used to view stained cells. against brighter, backlit background. From the Virtual Microbiology Classroom on Science. Prof. Online. com Image: Magnifying lamp use to look for part defects, US Navy; Compound light microscope, Moisey

Parts of a Compound Light Microscope Arm Ocular Lens Revolving Nosepiece Coarse Focus Objective Lens Stage Condenser Fine Focus Illuminator Base From the Virtual Microbiology Classroom on Science. Prof. Online. com Image: Compound light microscope, Moisey

Stereoscopic (Dissecting) Microscope • Used for viewing live specimens or threedimensional objects too large or thick to be accommodated by compound microscopes. • Not as powerful as compound microscopes

Microscopy: Electron Microscopes • • Used to observe VERY small objects: viruses, DNA, parts of cells Uses beams of electrons rather than light Many microscopic images in your textbook were obtained using electron microscopes. Electron beam wavelengths are shorter than light wavelengths, so better resolving power. • Transmission Electron Microscope (TEM): 2 -D image • Scanning Electron Microscope (SEM): 3 -D image Images: Poliovirus, taken with TEM, PHIL #1875, Blood cells, taken with SEM, National Cancer Institute; Scanning electron microscope, Geological Survey of Israel laboratory. From the Virtual Microbiology Classroom on Science. Prof. Online. com