i

K325 CELL BIOLOGY LABORATORY Exercise 1: Introduction to Microscopy

\Jj~Specimenf:r:::::r _Condenser

) " diaphragm

I Lamp field ,1 /stop -( )

~Collector

~ / Light source

(a) (bl -< FIGURE 5-5 The optical pathway Objective in a compound optical microscope. n (a) The specimen is usually mounted on a transparent glass slide and positioned Lens on the movable specimen stage of the microscope. Light from a bright source is focused by the collector and con

Specimen denser lenses onto the specimen. The it;I }voP;.c. objective lens picks up the light transmitted by the specimen and focuses it on the focal plane of the objective lens,

' 1 ~ Focal plane creating a magnified image of the speciI of objective men.' This image can be recorded

, lens\ directly. Usually, though, the image on ~.! the objective focal plane is magnified by t f\ the ocular lens, or eyepiece, which is

(c) focused on this objective focal plane; it w;obiective

Reflecting

Base withlight source

Ocular lens(eyepiece)

--/--\-..--+-- Condenser lens

picks up the light emanating from the already magnified image of the specimen and projects it onto the plane of

prism the human eye or a piece of photographic film. The lamp field stop, the condenser diaphragm, and the other apertures restrict the amount of light entering or leaving a lens. (b) An important parameter is the half-angle, a, of the cone of light entering the objective lens from the specimen. The larger the value of a, the finer the resolution the objective lens can provide. (c) Diagram of a modern compound microscope. {Parts (a) and (b) adapted from 8. Wilson, 1976, The Science and Art of Basic Microscopy, Figures 3-9 and 3-6.1

tyOVlA Lo&1~ A alL .

tJ -;:. rekctl \ie. \'~.)C. I- -::: VJet \J