MICROSC
OPY &
CELLS
WHAT I
WILL
❏ Parts and functions of a microscope
LEARN
❏ Total Magnification
and Actual size of specimen
❏ Biological drawing magnification
TABLE
OF
PARTS
&
0
FUNCTION
02
CONTENTS
CALCULATI
1
OF A
MICROSCOPE
Objective lens, Ocular lens
ONS
Total magnification &
Actual size of a specimen
03
BIOLOGICAL
DRAWINGS
Learn to draw and label
0
1
OF A
MICROSCO
PE
IDENTIF
Y THE
PARTS
OF A
MICROS
COPE
HOW THE
MICROSCOPE WORKS
The surface of the lens in the compound microscope is convex (curved
outwards), the light is bent, and the rays converge on a focal point. Beyond the
focal point, the rays spread out again (magnifying the image) and an inverted
image is formed in front of your eyes.
LOOKING
THROUGH
A
1) The specimen is placed on the stage
MICROSCOPE
2) Your eye will view it through 2 lens
● Eyepiece/Ocular lens
● Objective lens (3 different magnifications:
4x, 10x, 40x)
CALCULA
TIONS
02
CONVERS
IONS
1 cm = 10mm
1 cm = 10,000µm
If the drawing size is 10.5cm, how many
micrometres (µm) would that be?
TOTAL
MAGNIFICAT
ION =
MAGNIFICATION OF EYEPIECE LENS
X
MAGNIFICATION OF OBJECTIVE LENS
QUESTIO
N:
EYEPIECE LENS: 10(X)
TOTAL MAGNIFICATION: 40(X)
WHAT IS THE MAGNIFICATION OF OBJECTIVE
LENS?
THINK
So how
do we find out the actual
ABOUT
size of the specimen?
IT...
Actual Size (mm) = Image size (mm)
Magnification
PRACTICE
:
The image you are looking at is 1.5 mm long and you are using a
magnification of 100. Write down the calculation you would use to
work out the actual size of the object.
OBSERVED
In one of the oculars on your microscope,
SIZEis an ocular scale (GRATICULE).
What you see through the lens
SPECIMEN
MEASUREME
GRATICULE:
Scale printed onto the NT
eyepiece lens of the
microscope
SPECIMEN
MEASUREME
NT
SPECIMEN
MEASUREME
NT
**MEMORISE THIS TABLE!**
Objective
Lens
Total
Magnification
Graticule
scale
interval
4X
40X
25𝝁m
10X
100X
10𝝁m
40X
400X
2.5𝝁m
Note: 1000µm = 1mm
PRACTICE:
Actual size = no. of divisions on eyepiece
graticule x graticule scale interval
This image is viewed at 40x objective lens.
Width of plant cell is 24 eyepiece graticule
interval.
Actual size =
PRACTICE:
Actual size = no. of divisions on eyepiece
graticule x graticule scale interval
This image is viewed at 40x objective lens.
Width of plant cell is 24 eyepiece graticule
interval.
Actual size =
24 divisions x 2.5µm = 60 µm
SUMMAR
Y
**MEMORISE THESE 2!**
Actual size = no. of divisions on eyepiece graticule x graticule scale interval
= _________ (divisions) x _________ (either 25/10/2.5µm)
Magnification of drawing: Image size(Drawing size)
Actual size
0
3
BIOLOGICAL
DRAWING
●
●
●
●
●
●
●
●
●
MAKING A
BIOLOGICAL
Large drawing on blank white paper
Use only pencil
DRAWING
Name + date at top right
Clean lines (no shading)
Label lines to the right drawn with a ruler
Labels horizontal on the right
No arrowheads
Underlined title below drawing
Calculations go below drawing
BIOLOGICAL
DRAWING
Wrong: no clean lines, a lot of shading
Correct: neat, solid line
Top: correct
BIOLOGICAL
DRAWING
✔ Clean lines
✔ Labelling lines do not cross
✔ No shading
Bottom: wrong
╳ Lines not clean
╳ Labelling lines cross
╳ Nucleus is shaded
CELLS UNDER A
MICROSCOPE
HOW TO
PREPARE A
https://youtu.be/RfaSyfDBQzU
SPECIMEN USING
HOW
TOMOUNT
PREPARE
WET
A(plant
SPECIMEN
cell):
https://youtu.be/i2x3MKSJez4
USING WET
Cheek cells under a
microscope
Leaf cells under a light
microscope
Onion cells under a light
microscope
Which cell structure is missing in the onion cell?
WHY?
RULES OF THE MICROSCOPE
1.
Using one hand, hold the arm of the microscope. The other hand would support the
base.
2.Remove cover, write the microscope & lab number on the top right hand corner of your
worksheet.
3.Plug the microscope into the power source and switch on the switch on both the power
source and microscope. (REMEMBER: 2 switches on, 2 switches off)
4.Ensure that the objective lens is at its lowest magnification (RED:4x)
5.Turn eye piece around to face you/stage, arm facing back.
6.Place sample on stage and clip it to secure.
Magnification lens
Coarse adjustment
knob
Fine focus knob
4x
√
√
10x
√
√
40x
X
√
How to magnify sample
1.
Look through eyepiece at low power, use coarse adjustment knob. Once sample is
located, use fine focus knob.
2.
Without adjusting anything else, move the objective lens to medium power. Use the
coarse adjustment knob first, followed by fine focus knob.
3.
Once the sample is found, to view at highest power (40x lens), ONLY use the FINE
FOCUS KNOB to focus image.
4.
Once sample is located, draw observations.
KEEPING
THE
MICROSC
OPE
1)
Turn to low power lens, remove slide.
2)
Turn off both switches.
3)
Turn eye piece back to arm.
4)
Coil wire around.
5)
Cover the microscope.
6)
Return back to cabinets.