EL CAMINO
INSTRUCTOR: K.VILLATORO
ASSIGNMENT
STUDENT’S NAME: ________________
MICROSCOPES
Our understanding of nature often parallels the invention and refinement of instruments that extend human senses to
new limits. The development of microscopes, for example, provided increasingly clear windows to the world of cells.
The type of microscopes used by Renaissance scientists, as well as the microscopes you will use during the labs, are
called light microscopes.
Light microscopes use light rays that are magnified and focused by means of lenses. You will be using two different
light microscopes: the dissecting microscope is designed to study entire objects in three dimensions at low
magnification and the compound microscope is used for examining small or thinly sliced sections of objects under
higher magnification than that of the binocular dissecting microscope.
TO DO:
- Go to this website http://www.cas.muohio.edu/mbi-ws/microscopes/compoundscope.html
- Click on Parts. You can click on each of the part to see the location of this part.
- Use this information to label the following microscope. Note: that the microscope on the website is not
the same model as the microscope that we will use in the lab but it is very similar and you should be able
to locate its parts. Parts to label on this figure: Eyepieces (ocular lenses), arm, nosepiece, diaphragm,
base, and stage.
Stage clips
Stage knobs
It is important to know the location of these parts so that you can use your microscope properly and be able to view
the specimens we will study. You also need to know what these parts do.
TO DO: Read the functions of each of the parts and answer the questions based on this information.
Eyepieces (ocular lenses): holds one set of lenses that provides some magnification (it magnifies 10 times) to the
specimen and is the place that you view your specimen.
Base: the flat surface of the microscope that rests on your table
Arm: this part provides a carrying handle. To carry the microscope grasp the arm with one hand and place your other
hand under the base.
Nosepiece: revolving device that hold the objectives. Turning the nose piece allows you to switch from one objective
to the next. To make sure the objective is in place, you should always hear a click sound.
Objectives: each objective has a lens that focuses the light and provides some magnification to the specimen. Your
microscope has three different objectives each with a different power of magnification.
Low power objective: this lens has the lowest magnification of the three (it magnifies 10 times). It is the
objective that you will use first to focus your specimen before you switch to the other objectives. This is also
the objective that should be in place before storing away your microscope. This is the shortest of the
objective lenses.
High power objective: this lens has a higher magnification than the low power objective (it magnifies 40
times). It is the objective that you will switch to view your specimen in greater detail.
Oil immersion objective: this lens has the highest magnification of the three (it magnifies 100 times) and it is
used in conjunction with immersion oil to view specimens. We will not be using this lens during our labs.
Coarse adjustment knob: this knob is used to bring the specimen into approximate focus; USED ONLY with the low
power objective.
Fine adjustment knob: this knob is used to bring object into final focus.
Diaphragm: controls the amount of light used to view the specimen. If the specimen is too clear you should reduce
the amount of light to allow for more contrast. If the specimen is too dark you should allow more light through the
diaphragm.
Light source: a lamp at the base of the microscope that directs a beam of light up through the specimen. There is a
switch next to it to turn it off and on. You should always turn the light off when you are not using your microscope.
Stage: holds and supports the microscope slides that contain the specimen to view.
Stage clips: hold the slide in place on the stage
Mechanical stage control knobs: two knobs on the stage. One knob controls forward/backward movement of the
slide, and the other controls right/left movement of your slide.
Questions:
1.
What part of the microscope do you use to view your specimen?
2.
Name the two parts of the microscope that provide magnification to your specimen?
3.
Which objective always should be in place, both when beginning to use the microscope and when putting it
away?
4.
What adjustment knob is used when the microscope is set in the high power objective?
5.
Which two parts should you use to carry your microscope?
6.
Which part of the microscope should you use to regulate the amount of light going through your specimen?
7.
Which part of the microscope should you turn off if you are not using it?
8.
Which part of the microscope do you put the microscope slide on?
9.
Which part of the microscope do you use to move the microscope slide?
10. What does a click sound tell you?
Total magnification
Magnification is an increase in the specimen’s apparent size compared to its actual size. The lenses in the microscope
allow us to view small specimens because they increase the size of the specimen’s apparent size. The compound
microscope uses two set of lenses (the ocular and the objective) to view the specimen, so to estimate the total
magnification, you need to take in account the magnification of the ocular times the magnification of the objective.
TO DO:
- Go to this website http://www.cas.muohio.edu/mbi-ws/microscopes/Magnification.html
- Click on figuring total magnification.
- Fill out the following table using the information provided here.
Objective in use
Objective
magnification
Ocular lens
Total magnification
(how many times is the
specimen’s image magnified)
Low power
High power
Field of view
A microscope’s field of view is the area visible through the lens. As you increase the magnification of the specimen by
moving from the low power objective to the high power objective, something happens to the field of view. To find out:
In the previous website click on “click here to see the image”. The images show a piece of leaf from the elodea plant
under different magnifications.
TO DO:
From your observations of these images, explain what happens to the field of view as you increase the
magnification?_______________________________________________________________________________
Microscope Specimens
During this lab you will encounter three different preparations of specimens to view under the microscope:
1.
Specimens that are already mounted in a slide: these have already been mounted on a microscope slide and
are ready to use. They have a label on the side so that you know what is on the slide.
2.
Specimens that you need to mount yourself but do not require any staining.
3.
Specimens that you need to mount yourself and require staining.
To learn how to prepare slides, do the following:
TO DO:
- Go to this website http://utahscience.oremjr.alpine.k12.ut.us/sciber00/7th/cells/sciber/slidepre.htm
- Read the text and answer the following questions:
1. What is the slide?
2. What is the cover slip?
3. When do you do use a wet mount?
4. List the 5 steps to do a wet mount?
1. _______________________________________________________________________________
2. _______________________________________________________________________________
3. _______________________________________________________________________________
4. _______________________________________________________________________________
5. _______________________________________________________________________________
5. When do you need to use protoslo?____________________________________
6. When do you need to use a stain?______________________________________
7. Which are the three stains mentioned in this website? ____________________________________