Biology Key Points Microscopy
Units of Measurement
Centimetre (cm) = 10 Millimetre(mm)
1 Millimetre = 1000 Micrometres(µm)
1 Micrometre = 1000 Nanometre (nm)
Magnification and formula
Magnification is how much an image is sized up compared to the actual size of the thing taken.
Eyepiece Magnification x Objective Magnification = Overall Magnification
e.g. x10 x x100 = x1000
Formula of Magnification: Image Size = Actual Size x Magnification
e.g. 3000µm = 5.22µm x x575
Orders of Magnitude
Sizes can be compared using orders of magnitude. They are shown in powers of 10. So, 10 times bigger =
1 order of magnitude, 100 times bigger = 2 orders of magnitude.
To do orders of magnitude, you must check that both values have the same units. Once they do, divide
the larger number by the smaller number.
If the answer is <10, same order of magnitude
If the answer Is nearly 10 – one order of magnitude
If the answer is near 100 – two orders of magnitude
e.g. 20m = 2000cm ÷ 2cm
= 1000
= 3 orders of magnitude
Image resolution and resolving power
The resolving power is the minimum measure of the ability to distinguish between two separate points
that are close together. The smaller the resolving power, the higher the resolution.
For example, a light microscope has a maximum resolving power of 200nm. An electron microscope has
a maximum resolution of 0.2nm.
Light Microscope
Consists of a light source, lens and the human eye. Can magnify things several hundred times. Maximum
resolution of 200nm. It is convenient, cheap, it uses low skill to operate, keeps the specimen alive but
has a low resolution and magnification
Units of Measurement
Centimetre (cm) = 10 Millimetre(mm)
1 Millimetre = 1000 Micrometres(µm)
1 Micrometre = 1000 Nanometre (nm)
Magnification and formula
Magnification is how much an image is sized up compared to the actual size of the thing taken.
Eyepiece Magnification x Objective Magnification = Overall Magnification
e.g. x10 x x100 = x1000
Formula of Magnification: Image Size = Actual Size x Magnification
e.g. 3000µm = 5.22µm x x575
Orders of Magnitude
Sizes can be compared using orders of magnitude. They are shown in powers of 10. So, 10 times bigger =
1 order of magnitude, 100 times bigger = 2 orders of magnitude.
To do orders of magnitude, you must check that both values have the same units. Once they do, divide
the larger number by the smaller number.
If the answer is <10, same order of magnitude
If the answer Is nearly 10 – one order of magnitude
If the answer is near 100 – two orders of magnitude
e.g. 20m = 2000cm ÷ 2cm
= 1000
= 3 orders of magnitude
Image resolution and resolving power
The resolving power is the minimum measure of the ability to distinguish between two separate points
that are close together. The smaller the resolving power, the higher the resolution.
For example, a light microscope has a maximum resolving power of 200nm. An electron microscope has
a maximum resolution of 0.2nm.
Light Microscope
Consists of a light source, lens and the human eye. Can magnify things several hundred times. Maximum
resolution of 200nm. It is convenient, cheap, it uses low skill to operate, keeps the specimen alive but
has a low resolution and magnification
