Soal Latihan dan Jawaban Reading Comprehension 90
Each advance in microscopic technique has provided scientists with new perspectives
on the function of living organisms and the nature of matter itself. The invention of the
visible-light microscope late in the sixteenth century introduced a previously unknown
realm of single-celled plants and animals. In the twentieth century, electron microscopes
(5) have provided direct views of viruses and minuscule surface structures. Now another
type of microscope, one that utilize x-rays rather than light or electrons, offers a
different way of examining tiny details, it should extend human perception still farther
into the natural world.
The dream of building an x-ray microscope dates to 1895, its development, however,
(10) was virtually halted in the 1940’s because the development of the electron microscope
was progressing rapidly. During the 1940’s electron microscopes routinely achieved
resolution better than that possible with a visible-light microscope, while the
performance of x-ray microscopes resisted improvement. In recent years, however,
interest in x-ray microscopes has revived, largely because of advances such as the
(15) development of new sources of x-ray illumination. As a result, the brightness available
today is millions of times that of x-ray tubes, which, for most of the century, were the
only available sources of soft x-rays.
The new x-ray microscopes considerably improve on the resolution provided by optical
microscopes. They can also be used to map the distribution of certain chemical elements.
(20) Some can form pictures in extremely short times, others hold the promise of special
capabilities such as three dimensional imaging. Unlike conventional electron microscopy,
x-ray microscopy enables specimens to be kept in air and in water, which means that
biological samples can be studied under conditions similar to their natural state. The
illumination used, so-called soft x-rays in the wavelength range of twenty to forty
(25) angstroms (an angstrom is one ten-billionth of a meter), is also sufficiently penetrating
to image intact biological cells in many cases. Because of the wavelength of the x-rays
used, soft x-ray microscopes will never match the highest resolution possible with
electron microscopes. Rather, their special properties will make possible investigations
that will complement those performed with light- and electron-based instruments.
Reading Comprehension 90
A new kind of microscope
The detail seen through a microscope
Sources of illumination for microscopes
Outdated microscopic technique
develop the electron microscope later on
understand more about the distribution of the chemical elements
see viruses directly
discover single celled plants and animals they had never seen before.
a type of microscope
the natural world
To explain how it functioned
To begin a discussion of sixteenth century discoveries.
To put the x-ray microscope in historical perspective
To show how limited its uses are
Funds for research were insufficient.
Materials used to manufacture x-ray tubes were difficult to obtain
The source of illumination was not bright enough until recently.
X-ray microscopes were too complicated to operate.
They will eventually change the illumination range that they now use.
They will eventually be much cheaper to produce than they are now.
They will probably replace electron microscopes altogether.
They will provide information not available from other kinds of microscopes.