Ch. 2.2: Magnification and Calibration
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Define the terms magnification and resolution.
Magnification: how many times larger the image is than the actual size of the object being viewed. Resolution : the amount of detail that can be seen. The higher the resolution the more details are visible.
What limits resolution?
It is limited by the diffraction of light as it passes though samples ( and lenses ). Diffraction is when light waves spread as they pass close to physical structures e.g. those in the specimen. The structures are very close to each other and the light reflected from individual structures can overlap due to diffraction. This means they are no longer seen as separate entities and detail is lost.
How can resolution be increased?
By using beams of electrons which have a wavelength thousands of times shorter than light. Electron beams are still diffracted but the shorter wavelength means that individual beams can be much closer before they overlap.
How do you calculate magnification?
Magnification = size of image / actual size of image
How do you convert between nanometers , micrometers and millimetres
1000 nanometres ( nm ) = 1 micrometer ( um ) 1000 micrometers ( um ) = 1 millimetre ( mm ) 1000 millimetres ( mm ) = 1 metre (m)
What are the different units you need to use in magnification calculations?
• need to measure the image in mm and convert to the smallest unit used in the problem • magnification does not have a unit of measurement ( just use x)