BIOL101A- Lab 5 : Microscopes

light microscope

a microscope that extends our vision around 1000 times os that objects as small as 0.1 micrometer ( 10^-7m) in diameter can be seen

electron microscope

a microscope that further extends the viewing capability down to 10A or 0.1nm (10^-9 m)

resolving power

the ability to distinguish detail

• increased by reducing the wavelength of the light used

magnify

zooming into objects 

numerical aperture (N.A.)

a value part of the lens system which is derived from a mathematical expression that relates the solid cone of light delivered to the specimen by the condenser lens and to the light gathered by the objective lens 

contrast

the differential absorption of light by parts of the specimen

cytochemistry (histochemistry)

the study of staining

1. resolution

2. magnification

3. contrast

what a good microscope is dependent on

ocular lens

the lens system looking through

• monocular 

• binocular

diopter adjustment ring

allows for independent focusing of that lens to compensate for differences between the eyes

body tube

the hollow housing of the microscope through which light travels from he objective to the ocular lens

nosepiece with objective lenses

3-4 lenses mounted on a rotating nosepiece or turret attached to the bottom of the body tube

• 4x - low power

• 10x - medium

• 40x - high dry

• 100x oil emersion

total magnification

product of the magnification of the ocular lens and the magnification of the objective lens

stage

horizontal platform which the microscope slide is placed

iris diaphragm lever

adjustable light barrier built into the condenser

• adjusts amount of light being focused onto the specimen

substage condenser

the condenser lens system, located under the stage, focses light on the specimen

light source

light source on the microscope 

base and body arm

structural elements of the microscope

coarse focus adjustment knob

movement allows large movement of the stage toward the objective lenses 

• only for 4x or 10x 

• bottom line

fine focus adjustment knob

changes the specimen to objective distance very slightly with each turn of the knob

• only high dry and high oil

• 40x 100x

• top arrow

parfocal

if the specimen is in focus at one magnification, the specimen will be close tot eh focal plane when a different objective lens is rotated into place

depth of focus

only part of a thick specimen is in focus at any one setting 

• high the magnification the thinner the depth of focus 

ocular ruler

in the ocular lens that is a small glass disc on which is superimposed on the image of the specimen to be measured

stage micrometer

how the ocular ruler is calibrated

• a standard ruler

refraction

the bending of light as it passes from one medium to another

stereoscopic microscope

• aka dissecting microscope

• contains 2 objective lenses for each magnification

• 2 ocular lens

• magnifications → 4x to 50x

Transmission Electron Microscope (TEM)

a vertical television tube with an electron gun at the top and the fluorescent screen at the bottom

specimen processing

an important step prior to the placement of the specimen in a TEM, which fixes the tissue to preserve structure