Variable, various, varied

The frame provides a mounting point for various microscope controls.

Very, the very(+сущ.), to vary

Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast.

Van Leeuwenhoek's home-made microscopes were very small simple instruments, with a single, yet strong lens.

6. Устойчивые словосочетания

According to, in accordance with

These entries are numbered according to the image on the right.

As high as/as many as/ as much as/ as littli as/ as low as

Numerical apertures as high as 1.6 can be achieved.

Due to

Due to the difficulty in preparing specimens and mounting them on slides, for children it's best to begin with prepared slides that are centered and focus easily regardless of the focus level used.

Compound microscopes are heavier, larger and more expensive than simple microscopes due to the increased number of lenses used in construction.

It took about 150 years of optical development before the compound microscope was able to provide the same quality image as van Leeuwenhoek's simple microscopes, due to difficulties in configuring multiple lenses. Still, despite widespread claims, van Leeuwenhoek is not the inventor of the microscope.

For example/for instance

Before development of Köhler illumination the image of the light source, for example a lightbulb filament, was always visible in the image of the sample.

The former

The former typically ranges from 5× to 100× while the latter ranges from 0.14 to 0.7, corresponding to focal lengths of about 40 to 2 mm, respectively.

The latter

The former typically ranges from 5× to 100× while the latter ranges from 0.14 to 0.7, corresponding to focal lengths of about 40 to 2 mm, respectively.

In addition

In addition the vast majority of microscopes have the same 'structural' components

In order to

Focusing starts at lower magnification in order to center the specimen by the user on the stage.

In turn

The whole of the optical assembly is traditionally attached to a rigid arm which in turn is attached to a robust U shaped foot to provide the necessary rigidity.

Rather than

By using interference rather than absorption of light, extremely transparent samples, such as live mammalian cells, can be imaged without having to use staining techniques.