Microscopes
Tools of a Biologist Light Microscopes: –Simple Microscope (Single Lens- Magnifying Glass (1600s) –Inventor:
Tools of a Biologist –Compound Microscope (2 lenses) –Robert Hooke (1600s)
Modern Compound Light Microscope PARTS
Field of View
Depth of Focus
Tissue Prep for Microscopy 1. Fixation 2. Embed in wax 3. Slice with Microtome, Mount on slide, Stain
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 Embedding Area Microtome Water bath with sliced wax/tissue
Tissue prep-Mount onto slides
How does a lens work?
Can’t see virtual images unless you look through a lens Virtual vs. Real Images
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 10x-125X 3D 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 100,000X Magnification Can’t view live organisms 3D Image Blast electrons at object
Red Blood Cells using a SEM
Application Gunshot Residue
Collect Residue
Transmission Electron Microscope 2D Image Can’t View live organisms 250,000X 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 Microscope Spectrophotometer
Application
Magnification of money to fiber and ink level CounterfeitGenuine
Application CounterfeitGenuine Absorbance of light by ink