Introduction to the light microscope

Introduction to the Light Microscope

Parts of a binocular microscope

Binocular body

Rotating Nose Piece (turret)

Stage clips for slidesObjective lenses

StageFine focus

Coarse focus

Condenser

Rheostat

Base

Y axisX axis

Stage adjustmentknobs

Light source

Condenser

Aperture iris diaphragmin condenser

RheostatControls brightness

Light source

Width control

Individual focus

Ocular Lenses

Bright-Field Microscopy

• Image is produced when light is passed through specimen.

• Contrast is improved with staining techniques

Image Production in a Compound Light Microscope

• Light from the source is focused on the specimen by the condenser lens.

• It then enters the objective lens, where it is magnified to produce a real image.

• The real image is magnified again by the ocular lens to produce a virtual image that is seen by the eye.

Total Magnification

• The amount of magnification is marked on each lens

• Total Magnification = Objective X Ocular

10X

40X

10x X 40x = 400x

Resolution• Resolution: clarity of image• Limit of resolution (resolving power): how far

apart two points must be for the microscope to view them as being separate

• Light microscope = 0.2 um

Numerical Aperture

• NA = lens’s ability to “capture” light coming from specimen to make image

• Oil immersion increases NA, therefore increases its resolving power.

• Hold cover slip at 45 degree angle• Slowly lower cover slip to prevent bubbles• (click on title above to view animation)

Making a Wet Mount