microscopes
TRANSCRIPT
Microscopy: The Science of the Microscope
The Invention of the Microscope
• Renaissance invention (Mid 1600s)• Credit for invention goes to Anton Van Leeuenhoek• Constructed simple curved glass lenses in combination
Improving the Microscope
• Robert Hooke• English biologist who discovered cells• Increased magnification with improved lenses
Modern Compound Light Microscopes
• Uses 2 lenses in combination to magnify an image
• Can view objects too small to be seen with unaided eye
• Object must be thin enough for light to pass through
• Can view living things
• Typical magnification 100x to 1000x
See page 17 of your packet for a detailed discussion of:• Parts and their functions• Proper use and handling• Procedures for making a wet mount
Pushing the Limits: Electron Microscopes
• A light microscope cannot be used to distinguish objects that are smaller than half the wavelength of light
• Any object with a diameter smaller than 0.275 micrometers will be invisible or, at best, show up as a blur
• Electrons are speeded up in a vacuum until their wavelength is extremely short, only one hundred-thousandth that of white light.
• Electron microscopes were developed in the 1930s
Electron Microscopes
• Uses a beam of electron to view the specimen (not light)
• Specimen viewed must be prepared in a vacuum (no air molecules) therefore living things cannot be viewed using this type of scope
• Magnifies up to 200,000x magnification
Scanning Electron Microscope
Scanning Electron Microscope or SEM
• Bounces electrons off the surface of the object
• Produces a 3 dimensional image of the object
Red Blood Cells
Blood Clot
Nerve Cells
Tongue with a Taste Bud
Sperm on Surface of Human Egg
The Split End of a Human Hair
Tooth Plaque
Transmission Electron Microscope
Transmission Electron Microscope
• Electrons pass through the object forming a one dimensional picture
• Allows one to view the inside of an object (ex. internal structure of a cell)
filamentous bacteria from the gut of a termite
Sperm heads from a stick insect
Salmonella Bacteria
Stereoscope
• Allows viewing of macroscopic objects with great detail
• Does not require light to pass through object
• Can view living things
• Typical magnification of 10X to 30X
Choosing the Correct Microscope
Microscope Lab Skills Review
Complete the microscope review activities on pages 41 and 43-44.