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A drop of water works like a magnifying glass on
a leaf
Different refraction of light in water and air
Did You Know?
The magnification of a light micro-
scope cannot be increased infinitely
through the skillful combination of
magnifying lenses.
There are limits to a light micro-
scope's resolving power. Resolving
power is understood as the distance
that two points can have between
each other and still be perceived
as two distinct points under the
microscope.
Understanding Optics
Why does a straw that is inserted into a glass of water suddenly have a break
where there was none before? This is because light diffuses differently in air than
in other environments — water in this case. When light strikes the surface of
water, a portion of the light is reflected at the water's surface. The rest of the light
that enters into the water changes its direction a little. It is said that the light is
refracted.
The light that is striking the leaf through a drop of water is first refracted, reflect-
ed on the surface of the leaf, and then makes its way through the water drop and
into the eye of the observer. Here, the light is refracted again in such a way that
the underlying leaf surface appears to be enlarged. People knew how to make use
of this characteristic of light quite some time ago by using the refraction of light in
a drop of water as a magnifying glass. This early water-based magnifying glass had
its limits, of course.
It was only with the invention of "artificial water drops" made of glass that it
became possible to perfect the magnifying glass. Biology was given a tremendous
boost through the invention of magnifying lenses, because details could suddenly
be observed that remained hidden to researchers before. If lenses' shapes are
changed (thickness, curvature of the surface, etc.), then their magnifying charac-
teristics change as well. The lenses in the objectives of your microscope differ from
each other, resulting in the different magnifications of the object.
Instead of changing the shape of the lens to achieve higher magnifications, how-
ever, it is also possible to simply use several lenses in series. In your microscope,
there are two lenses in the objective and one in the ocular.
So, in effect, you are looking at the image (enlarged by the objective) with a
magnifying glass (ocular). You get the total magnification of the microscope by
multiplying the individual magnifications of the lenses together. In most micro-
scopes, the individual magnifications can be found on the ocular and objective,
respectively. Sometimes, however, the total magnification is already indicated on
the revolving nosepiece.
When magnifying an object using a so-called lens system — in the case of your
microscope, the system consists of three lenses — something else happens in ad-
dition to the magnification: the image is upside-down. What is "up" in the object
is "down" in the view through the eyepiece. What is "left" on the slide is "right"
when looking through the microscope. You will quickly become accustomed to
this. After a short time, you will automatically move the slide upward when you
want to look at a detail further down.
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