Extension

Care and Use of the Microscope

What is a microscope?
The microscope was invented by Anton van Leeuwenhoek. We use what
is called a compound microscope to see slides. This kind of
microscope works by shining light through a really really thin slice of
whatever it is you want to look at. The slice is so thin that the light shines
through it the way light shines through a lampshade.
The microscope also has a bunch of lenses. These lenses are at the end of
the objectives and in the eyepiece (see diagram to find these things). These
lenses magnify the image from the slide, the same way a magnifying glass
magnifies things, except microscope lenses are very powerful, they
magnify things a lot more than a magnifying glass. The microscopes you
are likely to have can magnify what your see 100 to 400 times. Imagine
yourself 100 times as tall as you are now. If you are 5 feet tall, that would
make you 500 feet tall, or as tall as a building that is 50 floors high. That is
how much your microscope magnifies things.
The microscope has a place where you can put a microscope slide. A slide
is a piece of glass with a really really thin slice of tissue on it. Below the
microscope’s stage is the light. The light has an electrical cord that goes to
a plug.
How to Take Care of a Microscope
If you have to carry a microscope, make sure your teacher shows you how.
First, make sure the electrical cord is wrapped around the microscope. If it
isn’t, you could trip and fall. Always hold the microscope with two hands.
Hold the microscope by the arm in one hand. See the diagram to find the
arm. The arm looks a little like a handle, doesn’t it? Put the other hand
under the microscope, right on the place where the microscope sits on the
table. That way, you can be sure you won’t drop the microscope.
Microscopes are really expensive!
How to Use the microscope
Your teacher has microscope slides of human tissue and human cells all
set up and ready for you. All you have to do is look in the eyepiece of the
microscope and work hard to try to see cells in the slides. Be careful not to
touch any of the knobs when you first start out!
Steps in looking at a microscope slide:
1. Look at the diagram of a microscope on the next page. Find the stage,
the fine adjustment, the coarse adjustment, and the eyepiece. Now, find
them on the real microscope you have in front of you. It is important to
know where everything is, so you don’t turn the wrong knobs. If you do,
you could break the slide, so be careful! If you accidentally turn the wrong
knob, as your teacher to come over and get the slide ready for you again.
2. Put your eye to the eyepiece in the microscope (see diagram). Some
microscopes have a place for only one eye, some have a place for both
eyes. Practice a little bit so you can see the “picture” of the microscope
slide. You may have to practice a little to find out how far to put your eyes
from the microscope.
3. After you can see something in the microscope. Check to see if it is
blurry (out of focus) or nice and sharp and clear (in focus). If it is blurry,
you will have to turn the “fine adjustment” knob (see the microscope
diagram), but don’t touch any of the knobs until you are sure you know
which knob is the fine adjustment. This knob will help you adjust the focus
for your eyes. Everyone’s eyes are a little bit different! Turn the knob
really slowly. See if the picture gets any clearer. If it starts getting blurrier,
turn the knob the other way until the focus is nice and sharp.

How to see cells in microscopes slides
The cells you see under the microscope won’t look much like the
drawings you have seen in books. They will be really small, and you
won’t see all the organelles that are in the drawings. This is because the
organelles are very small, and scientists had to use special microscopes
called electron microscopes to see them.
Try to find the nucleus of a few cells. They will usually be purple. Why
do you think the nucleus is purple?
Do you see any other colors on the slide?
Do you think the colors you see are the real colors of the tissue? If not,
where did the colors come from?
Next, look for the cell membrane that surrounds one nucleus. It will be a
very fine line. The shape of the cell will be different in different kinds of
tissue. The shape of cells in the skin will be different from the shape of
cells in the liver. The size will be different too. Skin cells are bigger than
liver cells, for example. All the cells you look like are really small.
Is there a lot of space between the cells?
Remember the ear of corn analogy. Was there space between the kernels?
If there were a lot of space between our cells, how do you think we would
hold together?
What do you think would happen when you pushed on your skin if there
were a lot of space between the cells?
Is there anything that is different about the slide you are looking at and
the ear of corn?
How thin is the tissue on your slide, compared to the ear of corn?
How thin is the tissue on your slide, compared to a piece of paper?
Try again to find one cell. You may have to look at a one nucleus after
another to find one where the cell membrane is dark and easy to see. Once
you find one, finding more gets easier.
How big is the nucleus, compared to the rest of the cell?
Does it take up a lot of space in the cell, or only a little?