How much resolution do I need for a microscope?

Scott Coutts scott.coutts at med.monash.edu.au
Mon Jun 9 09:13:11 EST 2003



Harry wrote:
 >
 > How high is the magnification do I need to see the molecules and
 > atoms?
 >

You're not going to see the molecules and atoms with any microscope that
you can buy (they're available, but it's not something you could buy).

You're going to need the lowest power to see details on 'big' objects, 
for example, the ridges on your finger, ink dots on a newsprint sheet, 
mandible (jaw) parts of an ant, scales on a moth's wing... around 
10x-40x would be enough for that.

You're going to need fairly low power to see animal and plant cells. 
That means up to around 100x-400x. Also between this and the previous 
category are pollen grains. You're going to be able to see fungal cells, 
spores and the cells of the hyphae (the branched 'fuzzy' bits) at this 
sort of power, but they'll still look small.

For bacteria, you're going to need higher power, around 400-1000x. But 
bacteria are relatively boring to look at (and I'm a microbiologist!). 
You wont be able to see any details on them, and they must be stained 
for you to be able to see them at all. They're not all that interesting 
to look at under an optical microscope. So I wouldnt bother with them at 
this stage.

Remember that when people sell microscopes, they normally quote the 
eyepiece (typically 10x) and objectives (typically 4x, 10x, 40x, 100x). 
Multiply the eyepiece by the objective to work out the totoal power. 
I.e. the 100x objective with the 10x eyepiece will give 1000x (about as 
much as you'll get on a light microscope).

If you buy a research microscope, it will probably come with a low-, 
mid- and high-power objective. Usually 10x, 40x, 100x. They're usually 
fitted with a 10x eyepiece, so this will give you magnifications of 
100x, 400x and 1000x. If I was you, I'd try to get one with a lower 
power than 10. Usually this is 4x (gives you 40x at the lowest power). 
The reason for this is that sometimes you might want to look at 
something that is reasonably big, such as the example I gave you before 
- the mandibles of an ant. You wont be able to see them very well if the 
image is magnified too much (they wont fit in the view you see down the 
scope).

 > For example, a blood sample. I heard that slide is a lot of
 > investment after the purchase of a microscope.

What do you mean? Pre-prepared slides? I mean, samples already fixed and
mounted on slides? If I were you, I would not bother buying things to
look at - there's plenty to find in just about anything you can fit
under the scope! Pic a single root of a single water weed, and it will
be teeming with little things to look at, as well as the actuall
individual cells that make up the root etc.

 >
 > Can I find and borrow that from a local general public library? I am
 > located in northern Virginia--Fairfax county, close to Washington DC.
 >

Not sure... I'm from Australia (:




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