Microscopes

Biology Index

Where are we going with this? The information on this page introduces microscopes and their use.

Article includes ideas, images, and content from Troy Smigielski (2021-08)

Microscopes

(We should take a very close look at this! See what I did there?)

A microscope is… Okay, most people know what they are and that they allow us to look at very minute details. 

Microscopes are tools that make an enlarged image of something that is otherwise too small to see.

Microscopes differ. Not all are equal.

Microscopes have two important specifications

• Magnification - the power to increase an object’s size
• Resolution - the power to show details clearly

These specifications make a big difference! It's not easy to have BOTH high magnification and high resolution. But, ideally, a good, quality microscope will have strong magnification and high resolution.

Source

Microscopes have been around for a long time. A dude named Zacharias Janssen is credited with inventing the microscope. Later, Anton van Leeuwenhoek was acknowledged as being the first microscopist. 

Later still, Robert Hooke discovered and coined the term "cell" by using a microscope to examine cork.

Microscopic Cork Image

Types of Microscopes

There are three types of microscopes! Yeah, that's right! Three!

Compound Light Microscopes

The compound light microscope is the most common type. 

• Uses a mirror (or other light source) that directs light upward through the specimen and into the lenses.

• Specimens can be living or non-living

• Can magnify up to 1000x.

About the Compound Light Microscope…

 

The compound light microscopes has an ocular lens (the one your eye goes on) and 4 objective lenses (the ones that point at the object you are trying to see).

•  The ocular lens is always 10x.

• You only use one of the 4 objective lenses at a time. The objective lenses have different powers such as:

• Scanning lens = 4x 

 

• Low objective = 10x 

 

• High objective = 40x 

 

• Oil immersion = 100x

The total magnification is equal to the power of the ocular lens multiplied by the objective lens.

As you magnify the image, you see less and less of it (duh). What you can see is called the field of view.

Said differently, the field of view is the diameter of the what you can see. The field of view decreases as magnification increases. 

Parts of a compound light microscope…

1. Body tube

2. Revolving nosepiece

3, 4, 5. Objective lenses

6. Stage clips

7. Diaphragm

8. Light source

9. Ocular lens (Eyepiece)

10. Arm

11. Stage

12. Course focus adjustment knob

13. Fine focus adjustment knob

14. Base

Scanning Electron Microscope (SEM)

• Uses a stream of electrons (not light) to produce an image.

• Specimens are non-living

• Can magnify up to 100,000 x

• Creates a 3-dimensional image

Transmission Electron Microscope (TEM)

• Uses a beam of electrons (not light) to produce an image

• Specimens are non-living

• Can magnify up to 200,000 x

• Looks at interior of cells