Compound microscope

Definition

A compound microscope is an optical instrument that uses multiple lenses to achieve higher magnification for viewing small specimens. It typically consists of an objective lens close to the specimen and an eyepiece lens through which the viewer observes.

5 Must Know Facts For Your Next Test

1. Compound microscopes use two sets of lenses: objective and eyepiece.
2. The total magnification is the product of the magnifications of both lenses, usually specified as $M = M_o \times M_e$ where $M_o$ is the magnification of the objective lens and $M_e$ is that of the eyepiece.
3. The resolution limit depends on the wavelength of light used and the numerical aperture (NA) of the objective lens.
4. Commonly used in biological and material sciences to observe cells, bacteria, and thin sections of tissues.
5. Illumination can be either transmitted or reflected light, with transmitted light often used for transparent samples.

Review Questions

• What are the two main types of lenses used in a compound microscope?
• How do you calculate the total magnification achieved by a compound microscope?
• Why does the resolution limit depend on both wavelength and numerical aperture?

Related terms

Objective Lens:

The primary lens in a microscope closest to the specimen that provides an initial magnified image.

Eyepiece Lens: The secondary lens through which a viewer looks, further magnifying the image produced by the objective lens.

Numerical Aperture (NA): A measure of a lens's ability to gather light and resolve fine specimen detail at a fixed object distance.