Micro2microscopy

USING THE METRIC SYSTEM TO EXPRESS THE

SIZES OF MICROORGANISMS >The basic unit of length in the metric system, the meter (m), is equivalent to approximately 39.4 inches.

>A meter may be divided into 10 (101) equally spaced units called decimeters; or 100 (102) equally spaced units called centimeters; or 1,000 (103) equally spaced units called millimeters; or 1 million (106) equally spaced units called micrometers;

or 1 billion (109) equally spaced units called nanometers.

MICROSCOPES >A microscope is an optical instrument that is used to observe tiny objects, often objects that cannot be seen at all with the unaided human eye.

Simple Microscopes >A simple microscope is defined as a microscope containing only one magnifying lens.

Compound Microscopes >A compound microscope is a microscope that contains more than one magnifying lens.

>Hans Jansen and his son Zacharias are often

given credit for being the first to construct and use a compound microscope.

>Photographs taken through the lens system of compound microscopes are called photomicrographs.

>The compound microscope is also referred to as a compound light microscope because visible light (from a built-in light bulb) is used as the source of illumination.

>Two magnifying lens systems: 1. Ocular lens- X10 magnifying power

2. Objective lenses- X4, X10, X40, & X100

>Total magnification is calculated by multiplying the magnifying power of the ocular by the magnifying power of the objective being used.

>Resolving power is the distance between 2 objects at which they cease to be seen as separate objects.

>Objects can be examined with the compound light microscope that are as much as 1,000 times smaller than the smallest objects that can be seen with the unaided human eye.

>Other Types of Compound Microscopes: 1. Brightfield microscope– another name for the compound light microscope 2. Darkfield microscope- illuminated objects are seen against a dark background; used to diagnose syphilis 3. Phase-contrast microscope- used to observe unstained living

microorganisms

4. Fluorescence microscope- contains a built-in ultraviolet (UV) light source

Electron Microscopes - use an electron beam as a source of illumination and magnets to focus the

beam > Two Types of Electron Microscopes: 1. Transmission electron microscope 2. Scanning electron microscope