If you want to make an object close to you look bigger then you can use a magnifying glass. The glass, or lens as it is called, bends the light and the image looks bigger.

Spectacles are two lenses attached side by side to make smaller images like letters in a book look bigger.

If you want to make something look really big then you have to place one lens in front of another lens. This can be awkward so they are put into a scientific instrument called the microscope, the first being made circa 1850.

So this is what a microscope basically does.

Obviously there are refinements to the microscope which govern what you want to look at, and how large you want it to be.

A common error is to buy one with too high magnification.

The more a microscope magnifies an object, the smaller the part of it that can be seen at any one time. The smaller this area the more difficult it is to decide exactly what the object is.

If you read a newspaper with a too powerful magnifying glass then you will see one letter at a time when you want to see words so you can make sense of what you see.

Magnification
This is defined as the number of times larger the size of an image is than the original object. Hence x20 means it is 20 times bigger.

For example a fly’s wing magnified x1000 shows a fuzzy webbed area but magnified by under x20 you can see the gossamer texture.

However if you want to see a cross-section of the wing then you are taking on a delicate operation. The wing would need to be prepared cut and a slither inserted into a slide to hold it. You will now need a powerful magnification to study it.

Examples show that even individual human blood cells only need x500, and the only items needing x1000 are micro-tiny bacteria.

There are of course many types of microscopes and specialized accessories.

Basically there are two basic types of microscope.

Stereo microscope/monoscopes.
High-power/compound microscopes.


Stereo microscopes/monoscopes
A monoscope (monocular) has one eyepiece to look through like a magnifying glass. One eye has to be kept closed while you look down the only tube holding a lens.

What is confusing is the microscope which has two eyepieces should be called a binoscope (binocular) but it is rarely used as often as monoscope and microscope is the more usual term.

The popular choice when buying a microscope is for a binocular model, although there is no hard and fast rule and beginners often may find that a monocular (one eyepiece) microscope is better as they have difficulty with the inter-pupillary adjustment.

Stereo microscopes /monoscopes gives three-dimensional (3D) views of objects under low magnification typically between x20 and x40 as well as a much greater depth than a conventional compound magnification.

Their advantage is that samples may be examined in their natural state with little or no preparation.

Stereo microscopes /monoscopes are ideal for educationalists, naturalists, collectors and appraisers with a wide range of applications including animal and insect dissection natural history, botany, gems, coins, stamps minerals and precision viewing of any sort.

They are often used to prepare specimens before further study on a high-power/compound microscopes so they are not suitable for cellular or very high-power studies.

Stereomicroscopes are an ideal introduction to microscopy for teenagers or children who are able to look at any object instantly, and at a relatively low magnification which allows them to make sense of what they see.

Youngsters are often put off microscopes by being given a high powered model which requires slide preparation and takes a long time to get a result.

Toy microscopes which pass off as genuine microscopes should be avoided because, while the cheap price is the attraction, they use plastic lenses.

High-power/compound microscopes.
They have a much wide range of magnification between x40 and x1500 and can be monocular or binocular. They need a lens with a short focal distance to produce a high magnification and therefore a shallow depth of focus so the lens has to be placed near the specimen for it to be in focus. They are mainly used for studying materials prepared and placed as smears, section, etc, between a slide and a coverslip.

Thus they are used for the study of microscopic-sized objects or for slices (sections) of larger objects that are thin enough to be transparent as in cellular or bacterial studies.

High-power/compound microscopes have a more limited space and field of view than stereo microscopes /monoscopes. They are not suitable for viewing unprepared objects.

Trinocular Microscopes
Trinocular models have two eyepieces for normal viewing, plus a third phototube on which you can mount a camera without interfering with the normal operation of the microscope.

While it is possible to mount a camera on a monocular or binocular microscope, it is far better to use a trinocular microscope designed for camera work.