Microscopy: The Science of the Microscope

The Invention of the Microscope

• Renaissance invention (Mid 1600s)• Credited for invention: Anton Van Leeuenhoek• Constructed simple curved glass lenses in combination

Improvement of 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 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 electrons 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

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.