1. Microscopes
SC.912.L.14.4 Compare and contrast structure and function of various types of microscopes.

2. How do different types of microscopes work?
Essential Question
How do different types of microscopes work?

3. Use of Microscope
To magnify objects that cannot be seen with the naked eye
Resolving power
Ability of microscope to distinguish objects as separate – measured in nm and the lower the number the smaller the object that can be distinguished

4. Comparing Powers of Magnification
We can see better details with higher the powers of magnification, but we cannot see as much of the image.
Which of these images would be viewed at a higher power of magnification?

5. Types of Microscopes Dissecting microscope 3D images
Relies on light on top of image
Low magnification
Compound light microscope
Observe living things
Magnifies up to 2000 times
Resolving power – 500 nm
Compound Light Microscope

6. Types of Microscopes Electron Microscopes
Transmission electron microscope (TEM)
2-D image Magnify hundreds of thousands of times
Resolution as great as 0.2 nm
Scanning electron microscope (SEM)
3D image
Lower magnification than TEM
Sample must be frozen or embedded on plastic – not living
Electron beam wavelengths are shorter than light wavelengths, so better resolving power.

7. Transmission Electron Microscope (TEM)
Scanning Electron Microscope (SEM)

8. TYPES OF MICROSCOPES
Directions: Copy this table onto your composition book.
Light Microscope
Transmission Electron Microscope
Scanning Electron Microscope
Radiation Source
light
electrons
Electrons
Wavelength
400 – 700 nm
0.005 nm
Lenses
glass
electromagnetic
Electromagnetic
Specimen
living or non living
supported on glass slide
non-living supported on a small copper grid in a vacuum
non-living supported on a metal disc in a vacuum
Maximum Resolution
200 nm
1 nm
10 nm
Maximum Magnification
1500 X X X
Stains
colored dyes
impregnated with heavy metals
coated with carbon or gold
Type of Image
colored
monochrome (black & white)

9. How do you work out the magnification of your microscope?
Essential Question
How do you work out the magnification of your microscope?
Ocular magnification X Objective magnification

10. A Lens
Enlarges an image and bends the light toward your eye.

11. Eyepiece (Ocular) Lens
Usually has a power of 10 x

12. How to Calculate Total Magnification
Eyepiece (Ocular) Lens X
Objective Lens =
Total Magnification

13. What’s my power?
To calculate the power of magnification, multiply the power of the ocular lens by the power of the objective.
What are the powers of magnification for each of the objectives we have on our microscopes?

14. The Objective Lenses
Rotary nosepiece of your microscope has objective lenses attached.
You will always be looking through the ocular and objective lens simultaneously, so multiply ocular magnification x objective power to calculate the Total Magnification (xTM).
Shortest lens (red band) should have been pointing down when your scopes were last put away.
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port

15. Scanning Power Red band around it. Magnifies objects 4x.
Q: What is the Total Magnification? ____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port

16. Has yellow band around it.
Low Power
Has yellow band around it.
Magnifies objects 10x.
Q: What is the Total Magnification? ____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port

17. Q: What is the Total Magnification? ____ TM
High Dry
Has blue band around it.
Magnifies objects 40x.
Q: What is the Total Magnification? ____ TM
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Image: Microscope objective lenses, T. Port

18. Let’s give it a try ...
1 – Turn on the microscope and then rotate the nosepiece to click the red-banded objective into place.
2 – Place a slide on the stage and secure it using the stage clips. Use the coarse adjustment knob (large knob) to get it the image into view and then use the fine adjustment knob (small knob) to make it clearer.
3 – Once you have the image in view, rotate the nosepiece to view it under different powers. Draw what you see on your composition book/
Be careful with the largest objective! Sometimes there is not enough room and you will not be able to use it!
4 – When you are done, turn off the microscope and put up the slides you used.

19. Microscope Techniques
Making a wet slide
Add a drop of water to center of slide
Place object in water (do not let it get folded)
Use forceps to position coverslip (fingerprints will interfere)
Lower coverslip slowly to avoid air bubbles

20. Microscope Care Always carry with 2 hands
Only use lens paper for cleaning
Do not force knobs
Always store covered
Keep objects clear of desk and cords
Teacher demonstrates how to hold the microscope, where the lens paper is located and how to use it. Students will be invited to turn the knobs and observe the stage as it moves up and down. Teacher will demonstrate how to store the microscope.

21. PRACTICE QUESTIONS
What is the difference between a light microscope and an electron microscope?
If the ocular lens is 8x magnification and the objective lens is 20x, what is the total magnification?
Why should the coarse adjustment knob not be used with the high power objective lens?
Describe how to correctly prepare the microscope for storage.