Basic Microscopy

Resolution

Property of an objective to distinguish the distance between two points as separate and distinct.

Numerical Aperture

A measure of the resolution of an objective. An objective with a 0.15 N.A. permits you to distinguish 15,000 lines per inch. If you view 16,000 lines per inch specimen through a 0.15 N.A. objective, you will never see the lines as separate no matter how powerful the magnification.

Focal length

The distance from the center of the lens to a point where the parallel light rays is brought to a focus. It is a constant of the lens system.

Working Distance

The distance between the front lens of an objective and the surface of the specimen when it is in focus.

Parfocal

The optical and mechanical design where only slight refocusing with the fine focus knob is sufficient to obtain clarity when changing from one lens to another.

Remember!!

Platelet

Erythrocyte

Neutrophil

Concave Mirror

it is used when the source of light (natural or artificial) is of low density.

Plane Mirror

this is used when the source of light is very bright.