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.