1. Tools of a Biologist MICROSCOPY Two factors play an important role in microscopy: 1. Magnification compares real size of a specimen with the one viewed with microscope. 2. Resolution (resolving power) refers to the clarity of the specimen viewed under the microscope.

2. Tools of a Biologist COMPOUND LIGHT MICROSCOPE The most commonly used microscope. Cells and small organisms can be observed while they are still alive. Light microscopes are limited to about 1000 times magnification due to the limit of resolution.

3. Tools of a Biologist COMPOUND LIGHT MICROSCOPE Limit of resolution is the point of magnification beyond which images become blurry and lose detail. This occurs because light passing through a lens is scattered, making it hard to form a clear image. For standard light microscopes, the limit of resolution is about 0.2 micrometers.

4. COMPOUND LIGHT MICROSCOPE

7. Tools of a Biologist ELECTRON MICROSCOPES These microscopes use a beam of electrons and magnets instead of light and lenses. They have a shorter wave length (0.2 nanometers) than a light microscope. Because of the high-energy particles involved, these microscopes cannot view living specimens.

8. Tools of a Biologist Transmission Electron Microscope (TEM)  TEM transmits a beam of electrons through a very thinly sliced specimen.  TEM can magnify objects up to 1,000,000 times.  The electron beam can also be used to expose photographic film to produce a permanent image.

9. Transmission Electron Microscope (TEM)

11. Tools of a Biologist Scanning Electron Microscope (SEM) SEM get their name from a pencil like beam of electrons that scans back and forth across the surface of a specimen. Electrons that bounce off the specimen are picked up by detectors that provide information to form a three-dimensional picture. SEM can magnify objects up to 300,000 times.

12. Scanning Electron Microscope (SEM)

13. Tools of a Biologist Scanning Electron Microscope (SEM)

14. Tools of a Biologist PROBE MICROSCOPES A new class of microscopes d eveloped in the 1980s. They do not use lenses to produce images. These instruments trace the surfaces of a sample with a fine tip known as a probe. They are called scanning probe microscopes.

15. Scanning Probe Microscopes

17. Tools of a Biologist PROBE MICROSCOPES Scanning probe microscopes have made it possible to observe molecules and groups of atoms. Unlike electron microscopes, scanning probe microscopes do not require that specimens be placed in a vacuum.