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Microscopes and Magnification
Microscopes and Magnification
Magnification is the relationship between the size of the image and actual size of the object being magnified.
How big is a typical cell?
Cells are so small you can fit 10-100 of them next to each other in a millimetre! What piece of equipment do we use to see them?
Microscopes magnify things. What does that mean?
How big is the actual cell under this microscope?
How big does the cell appear in the image you see when you look in the microscope?
So the real cell is 0.03 mm and the image of the cell is 30 mm. How many times bigger is the image than the real cell?
You worked out this microscope's magnification like this 0.03 mm30 mm=1,000. What is the formula for working out magnification?
A) magnification=real object sizeimage size B) magnification=image sizereal object size
So you work out magnification like this magnification=real object sizeimage size
For example, if a cell is actually 0.03 mm big, but it appears to be 30 mm big in the microscope, then the magnification is ×1,000
How big is the real cell here?
What is the size of the cell in the microscope image?
Use magnification=real object sizeimage size to work out the magnification here.
In this case the image is 500 times bigger than the real cell
The image size is 40 mm and the real cell is 0.08 mm, so magnification=0.08 mm40 mm=500
What unit is the size of the cell given in here?
A) Millimetres B) Micrometres C) Nanometres
What unit is the size of the image of the cell given in?
Be careful about the units!
If the size of the real object and the size of the image of the object aren't given in the same unit, you have to make them the same unit before you calculate magnification.
What is the magnification here?
Here magnification is ×500
20μm is the same as 0.02 mm, so magnification=0.02 mm10 mm=500
Here you have the image size and the magnification
You want to find out how big the cell actually is.
How can you use magnification=real object sizeimage size to work it out?
A) real object size=image size×magnification B) real object size=magnificationimage size C) real object size=image sizemagnification
Now, use real object size=magnificationimage size to work out how big the cell actually is in mm
Here the image of the cell is given in μm. What unit is that?
How big is the image of the cell in mm?
How big is the image of the cell in cm?
Summary! We use microscopes to study cells and other objects that are very small
Microscopes magnify things - they make them appear bigger.
You calculate magnification like this
magnification=real object sizeimage size
Here the cell appears to be 30 mm big in the image, but in reality the cell is only 0.03 mm big. That means the microscope has magnified the cell ×1,000 in the image.
You can also calculate the size of the real object of you have the image size and the magnification
real object size=magnificationimage size
Remember that the image size and the real object must be in the same unit before you calculate
For example, you can't say 30 mm30 μm to find magnification - one is in micrometres and the other in millimetres!