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Types of microscopes and calculations

Types of microscopes and calculations

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Tutor: Vacha

Summary

Types of microscopes and calculations

​​In a nutshell

Microscopes are devices we can use to zoom in or magnify very small objects. They’re very useful in looking at cells, as they are so small that we can’t see them with the naked eye.



Types of microscopes

Microscopes are used to view cells in much more detail. Different types of microscopes will produce varying levels of detail about the structure of a cell and its components.


​​Light microscopes

Light microscopes shine a light from the bottom of the microscope upwards towards the lens that you look at the cell with. With light microscopes, you can identify some structures such as the nucleus or cell membrane. However, to identify smaller structures or the internal details of a structure, you will have to use more powerful types of microscopes.


Electron microscopes

Electron microscopes can magnify cells much more than light microscopes can. This means they enable you to see inside substructures like mitochondria and ribosomes. However, electron microscopes require the sample to be in a vacuum to work; because there is no air, the sample cannot be living. Therefore, we cannot investigate cellular processes using an electron microscope. Electron microscope images also are only black and white, although colour can be added digitally later.

Biology; Key concepts; KS4 Year 10; Types of microscopes and calculations
A: Image from light microscope, 1. Basic outline of nucleus, 2. Basic outline of mitochondrion.
B: Image from electron microscope, 1. Detailed image of the internal structure of nucleus, 1. Detailed image of the internal structure of mitochondrion.



Microscopy calculations

We can use microscope images to work out the size of the cell or substructures using the following formula:


​magnification=image sizeactual sizemagnification=\frac{image\ size}{actual\ size}



When using calculations, it is important that to use the correct units. When measuring image size, we usually measure in centimetres or millimetres. However, the actual size of a cell is much smaller - we measure these in micrometres (μm\mu m) or nanometres (nmnm). Therefore, we need to know how to convert between units. 


​​unit

equivalent unit

​1 cm1\,cm​​
​10 mm10\,mm​​
​1 mm1\,mm​​
​1000 μm1000\,\mu m 
​1 μm1\,\mu m​​
​1000 nm1000\,nm 


The conversion can be visualised as the following:

Biology; Key concepts; KS4 Year 10; Types of microscopes and calculations


Example

A cell is magnified 25002500​ times. On paper, the image of the cell measures 20 mm20\ mm in diameter. Determine the actual size of the cell in micrometres. 

​1 mm=1000 μm1\ mm = 1000\ \mu m​​


Substitute the numbers in, making sure that the mmmm​ unit measurement is converted into μm\mu m​:


2500=20×1000actual2500=\frac{20\times 1000}{actual}


Rearrange the formula to get the actual size:


actual size=20,0002500actual\ size = \frac{20,000}{2500}


Simplify:

actual size=8actual\ size = 8​


​Therefore, the actual size of the cell is 8 μm.‾\underline{Therefore,\ the\ actual\ size\ of\ the\ cell\ is\ 8\,\mu m.}​​


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Learn with Basics

Length:
Animal cells, plant cells, and unicellular organisms

Animal cells, plant cells, and unicellular organisms

How to observe cells under a microscope

How to observe cells under a microscope

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Types of microscopes and calculations

Types of microscopes and calculations

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FAQs - Frequently Asked Questions

What is the limitation of light microscopes?

How do light microscopes work?

What are microscopes?

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