Transcript Day 3_ Unit 1 Microscopes Basics Presentation

Microscopes
SC.912.L.14.4
Compare and contrast
structure and function
of various types of
microscopes.
Essential Question
How do different types of
microscopes work?
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
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?
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
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.
Transmission Electron Microscope (TEM)
Scanning Electron Microscope (SEM)
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
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
250 000 X
100 000 X
Stains
colored dyes
impregnated with
heavy metals
coated with carbon
or gold
Type of Image
colored
monochrome (black
& white)
monochrome (black
& white)
Essential Question
How do you work out the
magnification of your
microscope?
Ocular magnification X Objective magnification
A Lens
• Enlarges an image and bends the light
toward your eye.
Eyepiece (Ocular) Lens
Usually has a power of 10 x
How to Calculate
Total Magnification
Eyepiece (Ocular) Lens
X
Objective Lens
=
Total Magnification
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?
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
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
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
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
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.
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
•
•
•
•
•
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
PRACTICE QUESTIONS
1. What is the difference between a light
microscope and an electron microscope?
2. If the ocular lens is 8x magnification and the
objective lens is 20x, what is the total
magnification?
3. Why should the coarse adjustment knob not be
used with the high power objective lens?
4. Describe how to correctly prepare the
microscope for storage.