Microscopy

What is a microscope?

• A scientific tool that helps scientists see things that cannot normally be seen with the “naked” eye.

History• Hans and Zacharias

Janssens-1590s, Dutch Eyeglass Makers, Inventors – Early microscope was

composed of a tube with lenses at both ends

– Magnification ranged from 3X to 9X

History • Robert Hooke- 1635-

1703, English Chemist, Mathematician, Physicist, and Inventor – Improved the compound

light microscope and observed cork (bark of an oak tree) and coined the term cells. They resembled cells, which are rooms in monasteries.

History• Anton van Leeuwenhoek-

1632-1723, Wine Assayer, Surveyor, Cloth Merchant, Minor Public Official, and Inventor – Made the best one-lens

microscope of his time.– He observed bacteria

from teeth scrapings and protozoa from pond water. He called them “weebeasties” and “animalcules.”

Compound Light Microscope Anatomy

• Microscope

• Resources available from sciencespot.net– Diagram of Light Microscope– Microscope Quiz– Microscope Crossword Puzzle

Proper Microscope Care and Technique

• How do you carry a microscope?• Always begin focusing on which

objective?• Only use the fine adjustment

knob for which objective?• How do you properly store a

microscope?

Using a Microscope in Lab

• Always make sure the stage is all the way up when focusing and slowly bring the stage down.

• When on low power, use the course adjustment knob (the big knob)

• When on high power, use the fine adjustment knob (the little knob)

• NEVER use the course adjustment knob on high power!!! Why?STOP

Other Notes…

• Center the object in the field of view

YES!NO!

Other Notes…

• Microscopes are parfocal- you can focus on scanning objective and switch to low-power and high-power objectives with minor adjustments in focusing

• At higher magnification, less light appears to pass through a specimen

• Wet mounts are temporary

Other Notes…

• Modern light microscopes are limited to 2000X due to lens optics

• Or higher powers of magnification, different types of microscopes are needed- they DO NOT USE LIGHT

Effect of Changing Objectives from Scanning to Low to High

PowerMicroscope Property Effect on Image

Magnification

Resolution

Depth of View

Field of View

Working Distance

Types of Microscopes

Follow the following link:

http://www.cas.muohio.edu/mbi-ws/microscopes/types.html

Stereoscope/Dissecting Microscope

• Used in dissections• Images are NOT inverted

Scanning Electron MicroscopeSEM

• Sweeps a beam of electrons over the surface of a specimen

• Approx. 60,000X magnification (max.)

• Example

Transmission Electron Microscope (TEM)

• Aims a beam of electrons through a specimen

• Magnifies +100,000X

Scanning Tunneling Microscope/Probe (STM)

• Electrons flow from the tip of the probe and the surface of the specimen

• Magnifies up to 100 million times (100,000,000X)

• Can see the surface of atoms!