MICROSCOPES

MOST IMPORTANT TOOL OF THE LABORATORY FOR STUDYING MICROORGANISMS

TERMS

Magnification – ability to enlarge objects Resolution – ability to show detail Contrast—the number of visible shades in a specimen

PRINCIPLES OF LIGHT MICROSCOPY Magnification Microscope has two magnifying lenses Called compound microscope Lens include Ocular lens and objective lens Most bright field scopes have four magnifications of objective lenses, 4x, 10x, 40x and 100x Lenses combine to enlarge objects Magnification is equal to the factor of the ocular x the objective 10x X 100x = 1,000x

EFFECT OF MAGNIFICATION

PRINCIPLES OF LIGHT MICROSCOPY Resolution Resolving power determines how much detail can be seen Resolution is enhanced with lenses of higher magnification (100x

TYPES OF MICROSCOPES

COMPOUND LIGHT MICROSCOPE Light Microscopy Light passes through specimen, then through series of magnifying lenses Most common and easiest to use is the compound light microscope

COMPOUND LIGHT MICROSCOPE

PATHWAY OF LIGHT

Principles of Electron Microscopes Uses electromagnetic lenses, electrons and fluorescent screen to produce image Resolution increased 1,000 fold over compound light microscope Magnification increased to 100,000x Two types of electron microscopes Transmission Scanning

Types of Electron Microscopes Transmission Electron Microscope (TEM) Used to observe fine detail Directs beam of electrons at specimen Electrons pass through or scatter at surface Shows dark and light areas Darker areas more dense Specimen preparation through Thin sectioning Freeze fracturing or freeze etching

Types of Electron Microscopes Scanning Electron Microscope (SEM) Used to observe surface detail Beam of electrons scan surface of specimen Specimen coated with metal Usually gold Electrons are released and reflected into viewing chamber Some atomic microscopes capable of seeing single atoms