Post on 04-Jan-2016
MICROSCOPESHow to Use a Microscope
Microscope Drawings
Parts of the Microscope
Magnification, Resolution and Contrast
Types of Microscopes
HOW TO USE A MICROSCOPE
see handout for complete list
carry microscope with care using two hands only use coarse adjustment on LOW power return microscope with stage as low as
possible, LOW power lens in place and power off
MICROSCOPE DRAWINGS
see handout for complete list
use pencil and white paper use a ruler for all labels and place them on
the right of the drawing use appropriate size and scale stippled when required
PARTS OF A COMPOUND LIGHT MICROSCOPE 1 – eyepiece/ocular –
contains the magnifying lens to look through
2 – body tube – holds the lenses of the eyepiece and the objectives at a set distance from each other
3 – high-power magnification lens – used to magnify the specimen 40 x and see a small area with lots of detail
PARTS OF A COMPOUND LIGHT MICROSCOPE 4 – low-power
magnification lens –used to magnify the specimen 4 x and see a large area with little detail
5 – stage clip – holds the slide in place
6 – stage – holds the slide and a hole in the center admits light
7 – diaphragm – regulates the amount of light that passes through the hole and the specimen
PARTS OF A COMPOUND LIGHT MICROSCOPE
8 – base – supports the weight of the microscope
9 – arm – supports the body tube and adjustments and allows the microscope to be carried
10 – coarse adjustment knob – used to get the specimen in focus
PARTS OF A COMPOUND LIGHT MICROSCOPE 11 – fine adjustment
knob – used to focus through the layers of the specimen
12 – revolving nosepiece – holds the objective lenses and permits their interchange
13 – light source –emits light through the diaphragm
MAGNIFICATION
amount the lens enlarges the specimen
in a compound light microscope both the eyepiece and the objective lenses magnify the specimen
total magnification is the amount of magnification seen when looking through both lenses
total magnification = eyepiece magnification x objective magnification
MAGNIFICATION
Calculate the total magnification for the school microscopes:
Eyepiece Magnification
Objective Lens Magnification
Total Magnification
10 x 4 x (Low Power)
10 x 10 x (Medium Power)
10 x 40 x (High Power)
RESOLUTION
how well a microscope allows you to make out two different objects that are very close together
most people can see with a resolution of 0.1 mm or larger
microscopes allow us to see with a higher resolution
CONTRAST
how well you can tell the difference between cell parts or the cell and the background
to improve contrast scientists will stain cells
stains allow scientists to see the cell against the background of light
most common stains used are methylene blue and iodine
SIMPLE LIGHT MICROSCOPES
uses one magnification lens
beam of light travels through the specimen
living organisms
movement
true colour
magnification of 1000x
SIM
PLE L
IGH
T M
ICR
OS
CO
PE
COMPOUND LIGHT MICROSCOPES
uses two magnification lenses
beam of light travels through the specimen
living organisms
movement
true colour
magnification of 2000x
resolution of 200 nm
CO
MP
OU
ND
LIG
HT M
ICR
OS
CO
PE
PA
RA
MEC
IUM
CELLS
– LIG
HT M
ICR
OS
CO
PE
CH
EEK
CELL – L
IGH
T M
ICR
OS
CO
PE
STEM
CELLS
– LIG
HT M
ICR
OS
CO
PE
TRANSMISSION ELECTRON MICROSCOPE
beam of electrons travel through the
specimen
only very thin specimens
specimens are encased in plastic and the
plastic is shaved to get the thickness
required
dead organisms
magnification of 5 000 000x
resolution of 0.2 nm
ELEC
TR
ON
MIC
RO
SC
OP
E
CELL – T
RA
NS
MIS
SIO
N E
LEC
TR
ON
M
ICR
OS
CO
PE
SCANNING ELECTRON MICROSCOPE electrons scan the surface of the specimen
and are reflected and magnified onto a screen to produce an image
image is 3-D
magnification and resolution lacking compared to transmission microscope
better contrast and depth than the transmission microscope
magnification of 300 000 x
resolution of 10 nm
AN
T – S
CA
NN
ING
ELEC
TR
ON
MIC
RO
SC
OP
E
EG
G C
ELL A
ND
FO
LLIC
LE – L
IGH
T
MIC
RO
SC
OP
E
EG
G C
ELL A
ND
SU
PP
OR
T C
ELLS
– S
CA
NN
ING
ELEC
TR
ON
SP
ER
M – L
IGH
T M
ICR
OS
CO
PE
SP
ER
M O
N T
HE E
GG
CELL – S
CA
NN
ING
ELEC
TR
ON