The Microscope

2 Types of Microscopes Light microscopes—also known as (aka) Compound light microscopes. These allow light to pass through the specimen and use two lenses to form an image. We use these in school. Electron Microscopes—focus beams of electrons on specimens. We can see specimens that are infinitesimal with these microscopes.

Compound Light Microscopes Micro-organisms can be seen using compound light microscopes It is called a light microscope

Light Microscope You can observe dead organisms (prepared slides) or live organisms with this microscope.

Electron Microscope 2 main types—a TEM or Transmission Electron microscope or and SEM- Scanning electron microscope. SEMs produce 3 dimensional images of a specimen. No live specimens! Dried

View through Microscopes-Which ones though?

Lenses It has 2 lenses— 1. Ocular lens- located on the eyepiece—magnification of 10X 2. Objective lens- has 3 different magnifications located on the bottom of the body tube—magnification anywhere from 5X up to 100X

Total Magnification To find the total magnification, you have to multiply the ocular lens (10X) by whatever magnification you use on the objective lens (40X) that would equal 400X magnification. What about if the objective lens were 50X? 70X? 100X? REMEMBER: the greater the magnification, the smaller the field of view. Do you increase the field of view when you increase the magnification?

Steps to Focus the Microscope 1. Always begin viewing the specimen with the low power objective (10X). 2. Focus by first moving the coarse adjustment-large knob used for rough focusing 3. Then use the fine adjustment-small knob used for final focusing on low power 4. Once the object is in focus, you can switch the objective lens to high power (40X or 100X). You may have to re-focus using the fine adjustment—small knob.

Wet Mount This is a technique used to prepare a biological sample for observation under a microscope Let’s say you wanted to see what Anton van Leeuwenhoek saw—you would use a Wet Mount!

Steps in a Wet Mount 1. Place a drop of freshwater on a clean slide. (when using dry specimens) 2. Use a dropper to place the specimen into the drop of water on the slide 3. GENTLY cover the specimen with a cover slip.

What you see… The image you see is not only ENLARGED, but it is also REVERSED and INVERTED (upside down) What about FR? How would that look? So if you want to see something right side up… A micro-organism that appears to be moving to the right on the slide is actually moving to the left or if moving toward you is actually moving away from you.