Microscopes & Math

https://pmt.physicsandmathstutor.com/download/Biology/A-level/Notes/OCR-A/1-Practical-Skills-in-Biology/PAG%2001%20-%20Microscopy.pdf

Magnification

How many times larger the image is than the actual size of the object being viewed

Resolution

The ability to see individual objects as separate entities

• Distance between 2 objects that can be easily distinguished

What is resolution restricted by - how to increase?

• Medium used e.g. light wavelength can only diffract a certain distance 

• Diffraction of light as it passes thru sample & lenses

Increase by:

• Using beams of electrons with wavelengths shorter than light

Calculating magnification 

size of image / actual size of object 

Conversion of units

Eyepiece graticule

• Etched into glass of eyepiece

• Calibrate for each objective lens separately

  • Relative size of divisions increases w. each increase in magnification

Stage micrometer 

• Microscope slide w. micrometeres scale engraved on it

• 100 divisions = 1nm, so 1 division = 10 micrometers

Calibrating eyepiece graticule

1. Line up eyepiece graticule w. stage micrometer 

2. Count no. of eyepiece units 

3. Count no. of stage micrometer divisions that align and multiply by 100 um

Working out using calibrated scale