Download fine adjustment knob - IBDPBiology-Dnl

The Light Microscope
The light microscope
Eyepiece lens
Nosepiece
Stage and
Stage Clips
Objective lens
Condenser
Coarse adjustment knob
Diaphragm
Fine adjustment knob
Light Source
Base
Parts of the microscope
Part of microscope
Eyepiece Lens
Function
Magnifies the specimen
Coarse Adjustment Knob Used to focus on Low Power
Fine Adjustment Knob
Used to focus on Medium and High Power
Objective Lens
Magnifies the specimen
Nosepiece
Allows the objective lens to be changed
Stage Clips
Holds the slide in place on the stage
Diaphragm
Controls amount of light entering condenser
Condenser
Concentrates light into a beam
Light Source
Projects light upwards through microscope
Total Magnification
• Microscopes have an eyepiece lens and several objective
lenses.
• These objective lenses are normally referred to as Low,
Medium and High Power.
Total Magnification = Eyepiece Lens x Objective Lens
Example:
Eyepiece Lens (x10)
Objective Lens (x4)
Total Magnification = (x10) x (x4)
= x40
Total Magnification
Eyepiece Lens
Objective Lens
Total Magnification
x10
x10
x100
x10
x40
x400
x10
x16
x160
x16
x10
x160
x16
x40
x640
x16
x16
x256
Field of View
• The field of view is the area of the slide which can be seen
when looking down through the microscope.
• The low power objective lens is ALWAYS used first because
this allows a larger area of the slide to be seen.
• This then allows you to choose which part of the specimen on
the slide you want to view in further detail at higher
magnifications.
•
Before increasing magnification the area you have chosen
should be moved to the centre of the field of view.
(N.B. The following slides demonstrate this.)
Low power
• Using the low power
objective lens and the
coarse adjustment knob
allows the word “BIOLOGY”
to be seen clearly.
• If we wanted to look at the
letters “BIO” more closely
then the slide has to be
moved so that these letters
are centre of the field of
view.
BIOLOGY
BIOLO
Medium power
• Using the medium power
objective lens and the fine
adjustment knob allows the
letters “BIO” to be seen
clearly.
• If we wanted to look at the
letter “B” more closely then
the slide has to be moved so
that this letter is centre of
the field of view.
BIO
High power
• Using the high power
objective lens and the
fine adjustment knob
allows part of the letter
“B” to be seen in more
detail.
Cells
• All living organisms are made of cells.
• Cells are the building blocks of life itself.
• Unicellular organisms:
consist of ONE cell.
e.g. amoeba
• Multicellular organisms:
consist of two or more cells.
e.g. earthworm
Animal Cells
• Nucleus
– Controls ALL of the
cells activities
• Cytoplasm
– Site of all of the
chemical reactions
• Cell Membrane
– Controls the entry
and exit of materials
•
•
•
•
Plant Cells
Nucleus
Cytoplasm
Cell Membrane
Cell Wall
– Made of cellulose, provides
support.
• Chloroplast
– Contains chlorophyll,
essential for photosynthesis
• Sap vacuole
– Contains solution of sugars
and salts
Slide Preparation and Staining
1. The material should be very thin to allow light to pass
through it. Some types of material can be smeared onto
the glass.
2. Most cell material is transparent and needs to be stained
with one or more coloured dyes. This makes different
parts of the cell stand out and easier to see.
3. The material should be covered with a coverslip to stop it
drying out. The coverslip should be lowered with a
mounted needle. This helps to prevent too many air
bubbles being trapped in the preparation.
Stains
Examples of coloured dyes or stains which can be used
to stain cells are:
a) Iodine stain
b) Methylene Blue stain
Onion cells under the microscope –
low power
Onion cells under the microscope –
medium power
Onion cells under the microscope –
high power
Magnified even further
Measurement
• Cells are so small that they cannot be measured
in millimetres !
• They are measured in micrometers (µm)
• There are 1000 micrometers in a millimeter.
1mm = 1000 µm
Converting to micrometers
• Convert the following measurements
from mm into µm (Show your working)
a.
b.
c.
d.
e.
f.
g.
h.
2 mm
0.5 mm
0.04 mm
1.06 mm
0.072 mm
0.123 mm
0.88 mm
0.022 mm
Converting to micrometers
a.
b.
c.
d.
e.
f.
g.
h.
2 mm
0.5 mm
0.04 mm
1.06 mm
0.072 mm
0.123 mm
0.88 mm
0.022 mm
x 1000 =
x 1000 =
x 1000 =
x 1000 =
x 1000 =
x 1000 =
x 1000 =
x 1000 =
2000 µm
500 µm
40 µm
1060 µm
72 µm
123 µm
880 µm
22 µm
Converting to millimeters
• Convert the following measurements
from µm into mm (Show your working)
a.
b.
c.
d.
e.
f.
g.
h.
3000 µm
250 µm
86 µm
900 µm
47 µm
505 µm
1050 µm
636 µm
Converting to millimeters
a.
b.
c.
d.
e.
f.
g.
h.
3000 µm
250 µm
86 µm
900 µm
47 µm
505 µm
1050 µm
636 µm
1000 =
1000 =
1000 =
1000 =
1000 =
1000 =
1000 =
1000 =
3mm
0.25 mm
0.086 mm
0.9 mm
0.047 mm
0.505 mm
1.05 mm
0.636 mm
Estimating Cell Size
160 cm
Can you estimate the size
of the frog?
Estimating Cell Size
To estimate the size of a cell you need to know:
• The diameter of the field of view
• The number of cells which fit across the
diameter of the field of view
Estimating Cell Size
Can you
estimate the
size
of the cell?
0.9 mm
Estimating Cell Size
Estimate of
cell size
Diameter of the Field of View
=
Number of cells that fit across
=
900 µm
6
=
150 µm
The estimated size of the cell is 150 µm.