IB Biology - The Microscope
Chapter 1.1 - Introduction to cells
Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
Resolution (Resolving Power)
From the above diagram, the resolving power decreases from left to right,
The Decrease the wavelength, the better the resolving power, the sharper the image
The light microscope possesses hardware including,
the coloured image given by the light microscope
Two magnifying lenses: eyepiece lens and objective lens in light microscope.
the wavelength of electron beam is much smaller than light, so TEM, SEM have much greater resolution
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)
you can see from the above image, the TEM (right) gives section image while SEM (left) gives the appearance of the pollen grain
Magnification and Scale
How to calculate the actual size of the specimen from the microscopy image?
e.g. you use a light microscope with 40x magnifying lens to view a cell with 10mm diameter in the image. The actual size of the cell:
(10x40) = 10mm / x
x = 0.025mm
the actual size is 0.025mm
Magnifying power of light microscopy = eyepieces lens x objective lens
In a microscopy image, you usually see a scale, how to calculate the actual size with the use of scale?
be awarded of the unit, "μm" is 1000x smaller than "mm" (1mm = 1000μm)
you can also calculate the magnifying power from the scale,
x = size of image / size of object
x = 60000μm / 39.96μm
In this IB biology topic, you have to know:
That is the end of the topics~~
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Written by Queenie l IBDP Biology Specialist @ TUTTEE
1. Quora. Retrieved URL from: https://www.quora.com/What-does-it-mean-by-resolving-power-of-a-microscope-and-telescope
2. IB Biology Syllabus. Retrieved URL from: http://ibbiology.wikifoundry.com/page/Calculate+the+linear+magnification+of+drawings
3. Major Differences. Retrieved URL from: https://www.majordifferences.com/2016/08/difference-between-sem-and-tem.html#.XqPIrpMzbjA
4. BBC. Retrieved URL from: https://www.bbc.co.uk/bitesize/guides/z9hyvcw/revision/2
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