1. Biology Unit C: Cycling of Matter in Living Systems
Chapter 1: Developments in Imaging Technology

2. A Window to a New World Agenda: Introduction to Microscopes
Uses for Microscopes
People involved in Scientific Discovery and Inventions/Improvements to Microscopes:
Aristotle
Hans & Zacharias Jensen
Robert Hooke
Antoni van Leeuwenhoek
Types of Microscopes
Parts of the Compound Light Microscope
Care and Use of the Microscope

3. Microscopes What do we use Microscopes for? Non-traditional uses:
To see anything that is difficult to see with the naked eye (plant parts, animal parts)
Non-traditional uses:
Solving crimes: (hair analysis, blood, other fluids)
Detecting crop diseases and pathogens
Detecting tiny defects in metal in bridges and airplanes
Detection of diseases like malaria and Tuberculosis
Use in Surgery (laparoscopic)

4. A Brief History So how did we come to use Microscopes?
It began with Scientific Inquiry – Asking questions about how things work
Early Greeks
Mostly philosophers – thinking out possible answers to problems rather than testing ideas
Aristotle (384 to 322 B.C.):
Followed a pathway of accurate observations and record making
Set up a classification system based on his observations
Reasoning and Interpretation followed the observations

5. A Brief History Hans and Zacharias Janssen Holland, ~1595
Father and son Dutch lens makers
Invented the compound microscope (2 lens system)
Magnifying power ~ 20 X

6. A Brief History Robert Hooke (1635-1703)
Used a hand made microscope with a 3-lens system
Recorded observations of plants, animals, and non-living objects
Viewed cork and saw many empty channels, which he called “cells” because they looked like Monks’ cells
Light was concentrated on the subject by passing it through a water-filled glass flask.
Early proponent of “biological evolution” due to his close observations of fossils.

7. A Brief History Antoni van Leeuwenhoek (~1665)
Identified different types of single celled organisms such as bacteria, sperm and unicellular protozoa
Highly skilled in making small lenses, and was able to produce higher magnifications than the compound microscopes of the day
A Replica of van Leeuwenhoek’s Microscope
Dutch business man who used a single lens microscope to see the movement of the different types of single cells.
Microscopic section through 1 year old Ash tree wood

8. Equivalent Measurement
Microscopes
Units of Measurement
Unit
Equivalent Measurement
Useful in Observing
Centimetre (cm)
1/100 metre; 10-2 m
Visible objects
Millimetre (mm)
1/10 centimetre; 10-3 m
Large particles or cells
Micrometre – also known as the Micron (µm)
1/1000 millimetre; 10-6 m
Majority of cells and their component parts
Nanometre (nm)
1/1000 micrometre, 10-9m
Large molecules and most cell parts
Angstrom (Å)
1/10 nanometre; 10-10m
Molecules and atoms
Now they have powerful enough microscopes to see strands of DNA or even individual atoms!

9. Microscopes Types of Microscopes
4 basic types of microscopes (in two categories):
Light Microscopes:
Dissection microscopes
Compound Microscopes
Electron Microscopes:
Scanning Electron Microscope
Transmission Electron Microscope

10. Light Microscopes Use light focused on the object to illuminate it
A thumb through a dissecting microscope
Use light focused on the object to illuminate it
Dissection microscope:
Image is 3-D, but it only has a low magnification, so you cannot see individual cells
Compound microscope:
Image is 2-D, but the magnification is powerful enough to see individual cells (with a low resolution)
Human hair at 100x mag.
Human hair at 400x mag.

11. Electron Microscopes
Use a beam of electrons, rather than light, to illuminate the object you are viewing
Scanning Electron microscope (SEM):
High magnification and high resolution, image is 3-D
Objects are coated in gold then the electrons bounce off the outside to give you a black and white image
Transmission Electron microscope (TEM):
Electron beams pass through thin specimens of the object, giving a 2-D image with high resolution at a high magnification
Synapse from a rat’s visual cortex

12. Compound Microscope
You will be using a compound microscope for your lab
You will need to know the different parts of the microscope and how to use it safely and carefully

13. Compound Microscope Revolving nosepiece Body tube Arm Objective lenses
Ocular lens (eyepiece)
Revolving nosepiece
Body tube
Arm
Objective lenses
Course adjustment knob
Stage
Fine adjustment knob appears below the course adjustment knob on your diagram in your notes
The iris diaphragm is right underneath the stage on your diagram
Stage clips
Power switch
Base
Light source
Note: Fine adjustment knob and iris diaphragm do not appear on this diagram

14. Parts of the Microscope
Eyepiece or Ocular Lens:
Has a lens that enlarges the image from the objective lens (usually 10X)
Course Adjustment Knob:
Brings the image into focus.
Used only with the low power objective lens
Fine Adjustment Knob:
Brings the image into focus with more detail
Used with the medium and high power objective lenses
Arm:
Supports the microscope
Use to help carry the microscope

15. Parts of the Microscope
Revolving Nosepiece:
Rotating mount that holds many objective lenses
Objective lenses:
Gathers light from a specimen and forms an inverted image
Low = 4X magnification
Medium = 10X magnification
High = 40X magnification
Stage:
Supports the microscope slide
Stage clips:
Holds the slide in place

16. Parts of the Microscope
Iris Diaphragm:
Controls the amount of light reaching the object
Light Source:
Sends light up through the object being viewed
Also called “lamp” or “mirror”
Base:
Supports the microscope
Also hold this when carrying the microscope (along with arm)
Power Switch:
Turns the light source on/off
May or may not be present on all microscopes

17. Care and Use (p. 5) Read the information before you start
Read the information before you start
Practice the skills you learn
Ask questions if you are not sure!
1. Always use 2 hands to carry the microscope! In the upright position with one hand supporting the base, and one holding the arm
2. Do not touch the lens with anything
3. Always check that the light switch is OFF before you plug it in
4. Always store your microscope with the stage lowered and the revolving nosepiece at its lowest point
5. Cover the microscope and return it to its storage place
6. YOU are responsible for cleaning your equipment (including the glass slides) after use. Use only lens paper to clean lenses.
7. Inform your teacher if your microscope does not work

18. Viewing Objects with the Microscope (p. 5)
1. Check that the stage is at its lowest point and turn the objective lens to the lowest power
2. Secure a prepared slide on the stage
3. While watching the stage raise it until the slide gets as close to the objective lens as it can without touching it
4. Look in the ocular lens while you use the course focus to LOWER the stage until the object comes into view. Fine focus is used to get a sharper image. Adjust the iris diaphragm if necessary
5. Turn to the medium power lens. Only use the fine focus adjustment under medium and high powered lenses!
6. Lower the stage and return the objective lens to the lowest power before removing the slide

19. A Look Ahead Next Class:
You will be using a microscope in pairs in the laboratory for class.
Bring your microscope handout, a pencil, and a ruler.
It’s also not a bad idea to bring your C1 booklet with the care and use instructions as well as the list of the parts of the microscopes