The microscope in cell studies
a) Differences between plant and animal cells
b, c, e) Magnification calculations
\(magnification = \frac{image size}{actual size}\)
d) Resolution and magnification
- magnification – how much bigger a sample appears to be under a microscope than it is in real life
- resolution – the ability to distinguish between 2 separate points.
– as resolution increases, image clarity and detail also increase
Types of microscopes
a) Light microscopes
• limit of resolution: half the wavelength
• ribosomes (25nm) can’t be seen with a light microscope as they don’t interfere with the light waves
• different stains are absorbed by different cell organelles so they can be observed more clearly
b) Electron microscopes
• vacuum (electrons cannot be focused without a vacuum as they will collide with air molecules and scatter)
• water boils at room temperature in a vacuum, so the sample must be dehydrated (specimen has to be dead)
Advantages of a light microscope over an electron microscope
1) can observe living tissue
2) more portable
3) easier to use – no technical training required
4) possible to see real/natural colours and a live specimen
5) can stain particular types of tissue for better visibility