Microscopes Tools of a Biologist Light Microscopes Simple

Microscopes

Tools of a Biologist • Light Microscopes: – Simple Microscope (Single Lens. Magnifying Glass (1600 s) – Inventor:

Tools of a Biologist – Compound Microscope (2 lenses) – Robert Hooke (1600 s)

Modern Compound Light Microscope PARTS

Field of View

Depth of Focus

Tissue Prep for Microscopy 2. Embed in wax 3. Slice with Microtome, Mount on slide, Stain 1. Fixation

Stains • Help visualize details of specimen – Vital Stains=Don’t harm living specimens (ex. Methyl Blue) – Lethal Stains=Kills Specimen (ex. Iodine)

Tissue Prep Center Microtome Water bath with sliced wax/tissue Embedding Area

Tissue prep-Mount onto slides

How does a lens work?

Virtual vs. Real Images Can’t see virtual images unless you look through a lens

Magnifying Lens • Virtual Lens

Real images can be seen directly without a lens -like those seen on a movie screen

Microscopes in Forensic Science • • • Compound Comparison Stereoscopic Polarizing Microspectrophotometer Scanning Electron Microscope

Stereoscopic Microscope • 10 x-125 X • 3 D Image • Right-side-up image • Most frequently used in crime lab • Wide field of view • Great depth of focus • Large working distance

Cheek Cells using Phase-Contrast Microscope No Stains Needed Can view live specimens

Scanning Electron Microscope 100, 000 X Magnification Can’t view live organisms 3 D Image Blast electrons at object

Red Blood Cells using a SEM

Application Gunshot Residue

Collect Residue

Transmission Electron Microscope 2 D Image Can’t View live organisms 250, 000 X Mag Blast electrons at object

Gunshot particles

SEM Coupled with X-Ray Analysis To Determine Elemental Nature of Residue

Blood Cells using a TEM

Confocal Laser Microscope

Comparison Microscope Compare: Bullets Cartridges Fibers Hairs

Polarizing Microscope

What’s an everyday use of polarized light?

Effect of Polarized Light • Analyzing minerals in soil • Analyzing synthetic fibers

Microspectrophotometer Spectrophotometer Microscope

Application

Application Magnification of money to fiber and ink level Counterfeit Genuine

Application Absorbance of light by ink Counterfeit Genuine