Cells, microscopes and creepy crawlies
description
Transcript of Cells, microscopes and creepy crawlies
Cells, microscopes and creepy crawlies
And all the other things you can’t see!
How small are they really?
E. coli: 2-3 μm
Influenza virus: 0.130 μm OR 130 nm
Red Blood cell: 8 μm
Onion cell: 250-400 μm
Let’s have a closer look!!!
1000 μm!!!
When you look in a microscope the circle of light that you see is called the ‘field of view’
Field of view
But how do we know how small a cell/specimen really is?It depends on the magnificationAs you increase the magnification the
field of view decreases
Measuring a cell!
Power Objective Lens magnification
Ocular Lens magnification
Total magnification
Field diameter (mm)
Field diameter (μm)
Low 4 10 40 4.0 4,000Medium
10 10 100 1.6 1,600
High 40 10 400 0.4 400
1000 μm!!!
1,600 μm
1,600 μm
Field diameter ÷ no. cells
≈ 533 μm ÷ 3
Measuring a cell!
Power Objective Lens magnification
Ocular Lens magnification
Total magnification
Field diameter (mm)
Field diameter (μm)
Low 4 10 40 4.0 4,000Medium
10 10 100 1.6 1,600
High 40 10 400 0.4 400
4,000 μm Low
Medium
High
4,000 μm ÷ 2
≈ 2,000 μm1,600 μm
1,600 μm ÷ 2
≈ 800 μm
400 μm
400 μm ÷ 2 ≈ 200 μm
Field diameter ÷ no. cells
We’re going to look at a few specimenDraw what you see Write down the magnification
Low = 4 × 10, Medium = 10 × 10, High = 40 × 10Guess how many of them you could fit side by
sideUse the formula to work out how long / wide
your specimen are!
Then we’ll come back to our tables to discuss what we found
Measuring your own specimens!