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magnification
Core and extended
Suppose you were to draw this ant
It’s a huge ant but we are going to say it is 10mm long
The drawing looks about three times the size of the ant
Let us check that more scientifically
We need to measure both the drawing and the ant
Using a ruler measure in millimetres
Measure the longest part but ignore appendages
Length of ant = 10mm
Measure the longest part but ignore appendages
Length of ant = 10mm
Length of drawing = 25mm
Magnification is calculated by:
MagnificationDrawn size
Actual size
= 25mm10mm
Units cancel
Mag X2.5
Length of ant = 10mm
Length of drawing = 25mm
Mag = 25mm10mm
Mag X2.5
Mag X2.5
Ask yourself “does this sound about right?”
In this example we are saying the drawing is magnified X2.5Or it is two and a half times bigger than the actual antAnd that seems about right!
If we draw something smaller than it actually is the magnification should be a fraction
Measure the length but not the shaft
Actual length = 80mm
Measure the length but not the shaft
Drawn length = 40mm
Mag = drawn sizeactual size
= 40mm80mm
Mag X1/2
In other words the drawing was half the size of the actual featherIt was magnified x1/2
Mag X1/2
That sounds about right
We can use a scale bar to find the actual size of an image
First we measure the scale bar
100µm = 20mm100µm = 20 000µm
Next we calculate how much the image has been magnified by seeing how much the scale bar is
magnified
100µm = 20mm100µm = 20 000µmThe scale bar is magnified20 000/100
=X200
What this means is the picture has been magnified 200 times
100µm = 20mm100µm = 20 000µmThe scale bar is magnified20 000/100
=X2000
Next we measure the cell we are interested in
100µm = 20mm100µm = 20 000µmThe scale bar is magnified20 000/100=200times
The cell is 17mmOr 17 000µm
Now we can find the actual length of the cell
100µm = 20mm100µm = 20 000µmThe scale bar is magnified20 000/100=200times
Mag = image size/ actual size
Actual size = image size/mag
= 17000µm/200= 85µm
This cell has a diameter of 85µm
Can you find the magnification of this cell using the scale bar provided?
Remember to convert mm to µm