Microscopes

History, Parts, and Usage

History of Microscopes• Microscopes were invented in late 1500s

– Compound microscope (2 or more lenses)– Used natural light, magified 20-30x

• Robert Hooke (1665)– Used a compound light microscope to look at

cork (dead oak cells)– Saw geometric shapes named them “cells”– Mechanical inventions (air pump, universal joint,

etc.) and medical experiments (blood transfusions, artificial respirators)

• Antony van Leeuwenhoek (mid1600s)– “father of microscopy and

microbiology”– Dutch tradesman (textiles)– built a simple light microscope

(one lens), but made great improvements (275x magnification)

– looked at water and saw protists, worms, rotifers, etc.

– also observed human blood and sperm

• Matthias Schleiden (1830s)– Concluded that all plants are

made of cells

• Theodore Schwann (1830s)– Concluded that all animals are

made of cells

• Cell Theory– All organisms are composed of

one or more cells.– The cell is the basic unit of

organization in organisms.– All cells come from pre-existing

cells.

• Electron Microscope (1940s)– Uses beam of electrons instead of light

– Magnifies up to 500,000x

– Two types:• Scanning electron microscope (SEM)

– See surfaces in 3D

• Transmission electron microscope (TEM)– See structures inside cells

History of Microscopes

• Scanning Tunneling Microscope (STM)– See atoms on surface of molecules– 100,000,000x

Let’s look more closely at one of our

microscopes…

Today’s Compound Light Microscope

• Uses lamp light

• Magnifies up to 1500x

• To calculate magnification:

eyepiece x objective (always10) (varies)

Example: If objective lens is set on 4x, what is the total magnification of

the microscope?

Microscope Usage Rules• Always carry microscope with one hand on

the arm and one hand on the base.

• Always look to the SIDE when LOWERING the objectives.

• Always begin viewing specimen on the LOWEST power, then work up.

• The coarse adjustment must only be used on the LOWEST power. Use fine adjustment on higher powers.