Investigating
cells
Total magnification
• In order to work out the TOTAL MAGNIFICATION of a
microscope we must multiply the power of the EYE PIECE LENS
by the power of the OBJECTIVE LENS.
Example:
The eye piece has a power of x10 and the objective lens has a
power of x35- The total magnification would be__________
Magnification
• If we know the TOTAL MAGNIFICATION we can use
DIVISION to work out the strength of the EYEPIECE LENS
or the OBJECTIVE LENS
Examples:
• The total magnification is 150 and the eyepiece lens is 10the strength of the objective lens would be _______
• The total magnifaction is 240 and the objective lens
strength is 100- the strength of the eye piece lens
is______
Cut and Stick..
1. Trim the edges from the worksheet
and glue it into your jotter
2. Complete the FIRST THREE COLUMNS
Real life size vs Apparent size
•We can work out an objects “apparent size” by
multiplying its ACTUAL size by the TOTAL
magnification.
Example- A cell has a diameter of 0.01mm, it is
viewed under a microscope with a total
magnification of x100- the apparent size of the
object is_____.
Real life size vs Apparent size
•We can work out an objects “actual size” by
multiplying its APPARENT size by the TOTAL
magnification.
Example- When viewed under the microscope, a
cell has a diameter of 16mm, the total
magnification of the microscope is x100- the
ACTUAL size of the cell is ________.
Worksheet
Complete the final two columns on the
worksheet you have glued into your
jotter
Micrometres, millimetres,
centimetres and metres
1 metre = 100cm
1 centimetre = 10 mm
1 mm = 1000 µm
Converting..
• In order to convert from micrometres (µm) to millimetres
(mm) we must MULTIPLY by 1000!
1 mm = 1000µm (1 x 1000)
1. How many micrometres are in 7.6mm?
2. How many micrometres are in 9.45 mm?
3. How many micrometres are in 30cm?
4. How many micrometres in 1 metre?
Converting..
• To convert from millimetres to micrometres we must DIVIDE
by 1000
1000µm = 1mm (1000/1)
1. Convert 14,000 µm into millimetres?
2. Convert 145,000 µm into centimetres?
3. Convert 600,000 µm into metres
Field of view
• In order to calculate the length of a
cell, we can COUNT the number of
cells along the DIAMETER of the
microscope then perform a
calculation.
If there are 8 cells in the FIELD OF VIEW
and the diameter is 2mm- How would
we work out the length of one cell?
Field of view
•How many cells?
•What is our calculation?
Diameter = 2mm
Field of view
•How many cells?
•What is our calculation?
Diameter = 3mm
Field of view
•How many cells?
•What is our calculation?
Diameter = 2mm
Observing cells
Preparing your slide: individual
1. Collect a small piece of onion and use the tongs to pull a
SINGLE layer from the inner surface
2. Put the piece of onion peel on your slide and flatten it out
3. Drop a few drops of iodine solution over the onion
4. Gently lower the cover slip making sure there is no air
bubbles
5. Show me your slide before looking at it under the
microscope
6. Draw what you see on page 10 of your printed notes
Think..
If onions are plants- why do
you not see chloroplasts?