Lab: Looking For Cells with a Microscope
Name __________________________ Date ______
In order to determine if an object is made of cells, scientists
examine it under a microscope. Magnification is a measure of how
much a microscope can enlarge what your are viewing. The compound
light
microscope multiplies the magnification of its eyepiece with an
objective lens. The best light microscope is capable of magnifying
objects 2,000 times.
The magnification of a microscope is limited by its resolving power,
which is based on the size of the waves of light used. Resolving
power is the ability to distinguish two closely applied points. The
resolving power of the normal unaided human eye is 0.1 millimeter. The resolution of a compound light
microscope is 0.2 micrometers (0.0002mm). At its highest magnification two objects can be no less than
0.2 micrometers apart without appearing as a single image. Any higher magnification and the two points
will blur into one. Using light to focus objects limits the resolution and therefore the magnification.
An electron microscope is capable of magnifying objects more than 200,000 times. Rather than using
light beams to illuminate objects it uses electron beams which have a much smaller wavelength, and so
increases the resolving power.
These are the important rules to follow to protect the microscope from being damaged.
1. Handle the microscope gently. Avoid bumping it and jarring it to protect the delicate alignment
of lenses inside.
2. Put down everything you are carrying before picking up a microscope.
3. Carry a microscope with two hands, one holding the arm and the other under the base.
4. Store the microscope on the lowest power setting with the cord wrapped around.
5. Always watch carefully as you move the higher power objective lenses.
6. Only use the fine adjustment to focus under high power.
7. Never leave a microscope slide on the stage when putting the microscope away.
8. To avoid scratching the microscope lenses, only use lens paper to clean them.
Fill in the gaps with the letter of the matching part.
Light source.
. The shortest objective (4X)
. Contains the ocular lens (10X)
. Anchors and moves the slide
. Revolves to allow you to switch objectives
. Low power objective
. Used for focusing in high power.
. Used for focusing in low and scanning power
. Where the microscope slide is placed for viewing
. One hand should grasp this part when carrying the microscope.
. Controls the amount of light passing through the specimen
. Magnifies 40X x 10X (ocular) times when clicked in place.
. One hand should be under this part when the microscope is carried.
. May be turned to allow the eyepiece of the microscope to be rotated.
Part 3. fill in the words to correctly complete the sentences.
1. Carry the microscope with one hand on the
Plug in the cord and
and the other on the
on the light.
2. Obtain a prepared slide and place it on the
3. Move the slide until the
in place. First, use the
. Now look through the
slowly until the
5. Then, center the
, anchoring it with the
appears to be directly on top of the
4. Always start focusing with the
the way
.
. Using the
.
in the center of the stage.
adjustment knob to move it stage all
adjustment knob,
the body tube
comes into view.
in the field of view . To adjust the light level, use the
6. To go to a higher magnification rotate the
objective in place. Use the
.
adjustment knob to
focus. You need to turn the knob only slightly to focus because when objects are in focus at one magnification ,
they will remain in focus at
in detail in the center of the
magnifications. Once again
the part of the image that you want to see
.
Teacher sign off _______
Objective: To learn how to use a compound light microscope to examine objects and identify cells.
Materials: compound light microscope, razor blade, glass microscope slide, coverslip, beaker of water,
pipette, forceps, scotch tape, stain. Lens paper.
Procedure: CHECK OFF EACH STEP AS YOU COMPLETE IT
____ 1. Learn rules to follow and the the parts and functions of the compound light microscope.
____ 2. Make a wet mount slide of your first object.
To make a wet mount slide, take a tiny sample of the object and place it on a glass microscope
slide. Add a drop of water on top of the sample. To prevent air bubbles from forming in your
slide, hold a cover slip at a 45 degree angle, and slowly lower it onto the slide.
_____3. Place the slide on the microscope stage and follow the steps for finding and focusing the object.
a. Place your slide on the microscope stage. Make sure the rotating nosepiece is set for the
smallest magnification objective lens.
b. Rotate the coarse adjustment knob to bring the objective lens as close as possible to the
slide.
c.
While looking into the eyepiece lens, slowly move the objective lens until it is in focus.
d. Move the slide to center the object within the larger circle of light called your field of view.
e. Call the teacher over to change to a higher magnification.
Teacher sign off _______
______ 4.
Write the steps you did to use the higher magnification:
______ 5. Once you have focused under the magnification that gives you the best view of the object,
draw and label.
What you see in the field of view. Label each microscope drawing. Do not
shade your drawings.
Analysis:
1.
What tool is necessary for scientists to determine if an organism is made of cells?
______________________________
1. A microscope slide prepared with wet ingredients is called a _________________
2.
Before you begin to focus the microscope should the objective lens be positioned close to the
specimen or far away from the specimen and why?
3.
The type of microscope we will use is called a Compound light Microscope. Explain how this
microscope works (based on its name)?
4.
Which objective lens must be used first and why?
5. How can you protect the microscope from damage?
6.
Why is the magnifying power of a compound light microscope limited?
7.
What do cells look like?