1

Use and Careof the

Microscope

The Compound Light Microscope

• has two magnifying lenses

• uses light for viewing

• most commonly used scope

ocularobjective

Ocular

Arm

Base

Nosepiece

Objectives Stage

Lightsource

Coarseadjustment

knob

Fineadjustment

knob

Stageadjustment

knobs

Stage

Iris diaphragm

On/off switch

When carrying a microscopealways use both hands

• one hand under the base

• one hand holding the arm

Carry the microscope close to your body

2

Magnification

Compound microscopes havetwo magnifying lenses

• ocular• objective

ocular X objective = totalmagnification

Ocular remains the same

Objectives rotate in nosepiece

Changing objectives changes total magnification

Each microscope has 3 or 4objectives on it

Each objective has its magnification written on it

There are only two objectivesused in this class

Totalmagnification =

10(ocular)

X 10(objective)

Low power objective (10X)

10/.25

Totalmagnification =

10(ocular)

X 43(objective)

High power or high dry objective

43/.6543/.65

3

Ability to see things clearlylimited by resolving powerTwo objects can be distinctlyseen only if they are far enoughapart for light to pass betweenthemDistance between two objects isresolving powerDepends on wavelength of lightand numerical aperture of lens

Field of view (field)

Lighted circle seen when lookingthrough the ocular

Depth of focusOn higher magnifications noteverything in field will be in sharpfocus--objects in different layers

Distance between objectiveand slide on stage

WorkingDistance

The Art of Focusing

• use coarse adjustment knobto get maximum working distance

• obtain a slide and place it onthe stage

• rotate the low power (10X)objective in place and use coarse adjustment to getminimum working distance

minimumworkingdistance

4

• use the stage adjustment knobsto position the slide over thehole in the stage

• look through the ocular

• use the coarse adjustment knobto focus on the slide

• the microscopes are parfocal

once they are in focus with oneobjective they are in focus forall objectives

• rotate the high power (43X)objective in place

• there is very little workingdistance--use only the fineadjustment knob to sharpenthe focus

• when finished viewing the slidemaximize working distance andremove slide from stage

• to view another slide start onlow power and repeat thefocusing process

• when finished for the dayclean the microscope

Cleaning the Microscope• remove the slide from the stage

• clean all lenses with lens paperand glass cleaner (if necessary)

• start with the ocular and endwith the oil immersion lens

5

• rotate the shortest (lowest power) objective in place and set at minimum working distance

• turn off light

• unplug microscope

• coil cord and tuck under rubberband on arm

• return to appropriate space onshelf