SCN1288-ABED_1: Lesson 1.1 - A Closer Look

Lesson 1.1 - A Closer Look

There are many things around us that we can not see because they are too small. Microscopes let us see many of those tiny things. Please read pages 158 and 159 in your textbook. Then answer the following questions.

Question 1. The Janssens' microscope was developed in 1590. How many times larger could it magnify a specimen?

Question 2. What are two differences between Anton van Leeuwenhoek's microscope and a modern compound microscope?

Question 3. What are the "beasties" that Leeuwenhoek saw in his microscope?

Question 4. How is an electron microscope different from a compound microscope?

Question 5. Name two types of electron microscopes. How are they different?

Then, return here to continue this lesson.

Enrichment and Interesting Facts

Microscopes can show us objects that are too small to see with our eyes and a telescope shows us things that are too far away. To see images of very distant and very small things go to this website:
http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

OR....Go to the Boston Museum of Science to see what an electron microscope looks like and see what it sees.....
http://www.mos.org/sln/sem/intro.html

Go to the next page to learn more about the microscope.....

Answers to Questions:

Question 1. The Janssens' microscope was developed in 1590. How many times larger could it magnify a specimen?

Check out the paragraph below picture 8.1, you will see that it could magnify specimens up to 30X. (The large X means "times" so thirty times larger).

Question 2. What are two differences between Anton van Leeuwenhoek's microscope and a modern compound microscope?

Leeuwenhoek's microscope has one lens.	The compound microscope has two lenses.
Leeuwenhoek's microscope could magnify about 200 X	The compound microscope can magnify 400 X to 1000 X
Leeuwenhoek's microscope used light from the room.	The compound microscope uses a light source or a mirror.

Here is a picture showing two antique microscopes and a compound microscope.

Question 3. What are the "beasties" that Leeuwenhoek saw in his microscope?

The beasties were probably bacteria, which are tiny microscopic living organisms.

Question 4. How is an electron microscope different from a compound microscope?

The electron microscope uses a beam of electrons to pass through the specimen. These are then focused by magnetic lenses and you view the images on a TV screen.

The compound microscope uses light from a mirror or light bulb to view the object. You look down inside the eye piece to see a clear image which the glass lenses focus for you.

Question 5. Name two types of electron microscopes. How are they different?

The transmission electron microscope (TEM) sends a beam of electrons at a thin slice of the sample. This sample can not be a living organism because it is first covered in special chemicals and then only a small slice used.

The scanning electron microscope (SEM) passes a beam of electrons over the whole body of the specimen. A metal coating on the specimen bounces back the electrons and gives a 3-D image of it.

to return to where you left off in this lesson.