2. The Microscope An optical instrument used for viewing very small objects invisible to the naked eye, typically magnified several hundred times.

3. Types of microscopes: Optical Microscope (also known as light or compound) Electronic Microscope –Transmission Electron Microscope (TEM) –Scanning Electron Microscope (SEM) –Scanning Tunnelling Microscope (STM)

4. Optical Microscope Most common and first invented Has one or more lenses Requires a light source (hence light microscope) Magnification of 400x

5. Body Tube Nosepiece Objectives Stage Clips Light Ocular lens (Eyepiece) Arm Stage Coarse Adjustment Fine Adjustment Always carry a microscope with one hand holding the arm and one hand under the base. Base Diaphragm

6. This type of microscope is termed “compound” because it magnifies a specimen using TWO lens system. The lens system located in the eyepieces is called the OCULAR system. The lens system located in the rotating turret is called the OBJECTIVE system. Compound Light Microscope

7. Microscope Magnification The magnification of the ocular (eyepiece) lens in most compound light microscopes is 10X.

8. Microscope Magnification There are 3 separate objective lenses on the revolving nosepiece. Their magnifications are: ( Ours only have 3 objective lenses)

9. Total Magnification When you view a specimen, you are using both the ocular lens and one of the objective lenses. Therefore, the total magnification of the specimen is the product of the power of the ocular lens and the power of the objective lens. Example follows

10. Total Magnification & Field of View 10X (ocular) x 40X (objective) = 400X The new total magnification would be: As the specimen is magnified, the field of view becomes smaller.

11. Comparing Powers of Magnification We can see better details with higher the powers of magnification, but we cannot see as much of the image. Which of these images would be viewed at a higher power of magnification?

12. Electronic Microscope Transmission (TEM): beam of electrons passes through a very thin slice of the specimen Scanning (SEM): a beam of electrons scans the surface of the sample Image appears on a screen (like a TV) Magnifications of 2 000 000 x!