I was practicing RC questions from Big Book /test 13/ Section 1 / passage 1 and I got Question no 20 and 23 wrong but not sure why I got them wrong. I was wondering if anyone has a link to something that explains the correct answers.
Passage:
Classical physics defines the vacuum as a state of
absence: a vacuum is said to exist in a region of space if
there is nothing in it. In the quantum field theories that
describe the physics of elementary particles, the vacuum
becomes somewhat more,complicated. Even in empty
space, particles can appear spontaneously as a result of
fluctuations of the vacuum. For example, an electron
and a positron, or antielectron, can be created out of the
void. Particles created in this way have only a fleeting
existence; they are annihilated almost as soon as they
appear, and their presence can never be detected directly.
They are called virtual particles in order to distinguish
them from real particles, whose lifetimes are not con
strained
in the same way, and which can be detected.
Thus it is still possible to define the vacuum as a space
that has no real particles in it.
One might expect that the vacuum would always be
the state of lowest possible energy for a given region of
space. If an area is initially empty and a real particle is ,
put into it, the total energy, it seems, should be raised by
at least the energy equivalent of the mass of the added
particle. A surprising result of some recent theoretical
investigations is that this assumption is not invariably
true. There are conditions under which the introduction
of a real particle of finite mass into an empty region of
space can reduce the total energy. If the reduction in
energy is great enough, an electron and a positron will
be spontaneously created. Under these conditions the
electron and positron are not a result of vacuum fluctua
tions
but are real particles, which exist indefinitely and
can be detected. In other words, under these conditions
the vacuum is an unstable state and can decay into a
state of lower energy; i.e., one in which real particles are
created.
The essential condition for the decay of the vacuum is
the presence of an intense electric field. As a result of the
decay of the vacuum, the space permeated by such a
field can be said to acquire an electric charge, and it can
be called a charged vacuum. The particles that materi
alize
in the space make the charge manifest. An electric
field of sufficient intensity to create a charged vacuum is
likely to be found in only one place: in the immediate
vicinity of a superheavy atomic nucleus, one with about
twice as many protons as the heaviest natural nuclei
known. A nucleus that large cannot be stable, but it
might be possible to assemble one next to a vacuum for
long enough to observe the decay of the vacuum. Experi
ments
attempting to achieve this are now under way.
Questions:
20. Physicists’ recent investigations of the decay of the
vacuum, as described in the passage, most closely
resemble which of the following hypothetical events
in other disciplines?
(A) On the basis of data gathered in a carefully
controlled laboratory experiment, a chemist
predicts and then demonstrates the physicaJ
properties of a newly synthesized polymer.
(8) On the basis of manipulations of macroeco
nomic
theory, an economist predicts that,
contrary to accepted economic theory, infla
tion
and unemployment will both decline
under conditions of rapid economic growth.
(C) On the basis of a rereading of the texts of Jane
Austen’s novels, a literary critic suggests that,
contrary to accepted literary interpretations,
Austen’s plots were actually metaphors for
political events in early nineteenth-century
England.
(D) On the basis of data gathered in carefully
planned observations of several species of
birds, a biologist proposes a modification in
the accepted theory of interspecies competi
tion.
(E) On the basis of a study of observations inciden
tally
recorded in ethnographers’ descriptions
of non-Western societies, an anthropologist
proposes a new theory of kinship relations
- The author’s assertions concerning the conditions
that lead to the decay of the vacuum would be most
weakened if which of the following occurred?
(A) Scientists created an electric field next to a
vacuum, but found that the electric field was
not intense enough to create a charged
vacuum.
(B) Scientists assembled a superheavy atomic
nucleus next to a vacuum, but found ,that no
virtual particles were created in the vacuum’s
region of space.
(C) Scientists assembled a superheavy atomic
nucleus next to a vacuum, but found that
they could not then detect any real particles
in the vacuum’s region of space.
(D) Scientists introduced a virtual electron and a
virtual positron into a vacuum’s region of
space, but found that the vacuum did not
then fluctuate.
(E) Scientists introduced a real electron and a real
positron into a vacuum’s region of space, but
found that the total energy of the space
increased by the energy
