Subatomic particles can be divided into two classes: fermions and boso

Question

Subatomic particles can be divided into two classes: fermions and bosons, terms coined by physicist Paul Dirac in honor of his peers Enrico Fermi and Satyendra Bose. Fermions, which include electrons, protons, and neutrons, obey the Pauli exclusion principle, according to which no two particles can inhabit the same fundamental state. For example, electrons cannot circle the nuclei of atoms in precisely the same orbits, loosely speaking, and thus must occupy more and more distant locations, like  a crowd filling seats in a stadium . The constituents of ordinary matter are fermions; indeed, the fact that fermions are in some sense mutually exclusive is the most salient reason why two things composed of ordinary matter cannot be in the same place at the same time.

Conversely, bosons, which include photons (particles of light) and the hitherto elusive Higgs boson, do not obey the Pauli principle and in fact tend to bunch together in exactly the same fundamental state, as in lasers, in which each photon proceeds in perfect lockstep with all the others. Interestingly, the seemingly stark division between fermionic and bosonic behavior can be bridged. All particles possess “spin,” a characteristic vaguely analogous to that of a spinning ball; boson spins are measured in integers, such as 0 and 1, while fermion spins are always halfintegral, such as 1⁄2 and 11⁄2. As a result, whenever an even number of fermions group together, that group of fermions, with its whole-number total spin, effectively becomes a giant boson. Within certain metals chilled to near absolute zero, for instance, so-called Cooper pairs of electrons form; these pairs flow in precise harmony and with zero resistance through the metal, which is thus said to have achieved a superconductive condition. Similarly, helium-4 atoms (composed of 2 electrons, 2 protons, and 2 neutrons) can collectively display boson-like activity when cooled to a superfluid state. A swirl in a cup of superfluid helium will, amazingly, never dissipate.

The observation that even-numbered groups of fermions can behave like bosons raises the corollary question of whether groups of bosons can ever exhibit fermionic characteristics. Some scientists argue for the existence of skyrmions (after the theorist Tony Skyrme who first described the behavior of these hypothetical fermion-like groups of bosons) in superconductors and other condensed-matter environments, where twists in the structure of the medium might permit skyrmions to form.    1 
 Consider each of the answer choices separately and indicate all that apply.

1. The example of “a crowd filling seats in a stadium” ( Highlighted ) is intended to

A. expand upon one consequence of the Pauli exclusion principle
B. illustrate a behavior of certain fermions
C. describe how electrons circle the nuclei of atoms in concentric, evenly spaced orbits

2  
 2. The author’s primary purpose in writing this passage is to

(A) explain the mechanism by which fermions can become bosons
(B) describe the two classes of subatomic particles
(C) provide examples of the different forms of matter
(D) explain the concept of particle “spin”
(E) argue that most matter is composed of one type of particle

3  
 3. Which of the following is not mentioned as a characteristic of bosons?

(A) They can be composed of groups of fermions.
(B) They are measured in integer spin.
(C) They are the constituents of ordinary matter.
(D) They tend to bunch together in the same fundamental state.
(E) They lead to phenomena such as superconductors and superfluids.

4  
 4. Which of the following can be properly inferred from the passage?

(A) An atom composed of two protons and a neutron would be considered a boson.
(B) Skyrmions have been discovered in superconductors and other condensed matter environments.
(C) Two electrons in an atom cannot circle the same nucleus at exactly the same distance.
(D) A current through a superconducting wire will never dissipate.
(E) Fermions cannot behave as bosons unless they are cooled to a temperature near absolute zero.

5  
 5. According to the passage, which of the following describes a difference between fermions and bosons?

(A) Fermions cannot inhabit the same fundamental state, whereas bosons bunch together in the same state.
(B) Fermions contain many more types of particles than bosons.
(C) Fermions exist in groups, but bosons do not.
(D) Fermions have integral spin values, whereas Bosons have half-integer spin.
(E) Fermions do not obey the Pauli principle, whereas bosons do.

6  
 6. Based on the information in the passage about the Pauli exclusion principle, to which one of the following situations would this principle be most relevant?

(A) Fermi Energy: The maximum energy that electrons in a solid will contain in order to avoid having identical energy levels
(B) Particle Accelerators: Devices that will accelerate charged particles to very high speeds through the application of an external magnetic field
(C) Quantum Entanglement: When particles interact physically and then become separated but still have interdependent properties
(D) Double Slit Experiment: An experiment that revealed the particle and wave duality of photons
(E) The Higgs Field: The field produced by the conjectured Higgs particle that would explain why matter has mass

Sajjad1994 · Answer

OE

1. The example of “a crowd filling seats in a stadium” (     Highlighted     ) is intended to

The words  “for example”  at the beginning of the sentence containing the crowd analogy follow a sentence about the Pauli exclusion principle. This principle says that fermions cannot  “inhabit the same fundamental state.”  Electrons, which are fermions, are likened to members of a crowd in a stadium; the fact that electrons cannot  “circle the nuclei of atoms in precisely the same orbits”  (just as crowd members cannot sit on top of one another) is a  “consequence”  of the Pauli exclusion principle. Thus, the first statement is justified. These electrons  “must occupy more and more distant locations” ; the crowd analogy certainly illustrates that behavior, so the second statement is justified. As for the third, incorrect statement, while it is true that electrons cannot occupy the same orbits as one another and must instead occupy more and more distant locations, you do not know that those orbits are  “concentric”  or  “evenly spaced.”  
  
  Answer: A and B

Sajjad1994 · Answer

OE

2. The author’s primary purpose in writing this passage is to

The author begins by naming the two classes of subatomic particles,  choice (B) , and then divides the remainder of the passage into descriptions of each class and their relation to each other. Regarding  (A)  and  (D) , the author explains both of these concepts within the passage, but they are subordinate to the main idea of describing the two types of subatomic particles and thus are not the primary purpose of the passage. As for  (C)  and  (E) , the author’s primary purpose in writing is not to provide examples or to argue. 
  
  Answer: B

Sajjad1994 · Answer

OE

3. Which of the following is not mentioned as a characteristic of bosons?

The author states that fermions, not bosons, are the constituents of ordinary matter. All other answers are mentioned in the second paragraph of the passage. Thus,  (C)  is the correct choice. 
  
  Answer: C

Sajjad1994 · Answer

OE

4. Which of the following can be properly inferred from the passage?

The second paragraph states that Cooper pairs of electrons will  “flow in precise harmony and with zero resistance through the metal.”  As an example of the same phenomenon, the second paragraph also states that a  “swirl in a cup of superfluid helium will, amazingly, never dissipate.”  Therefore, it is correct to infer that  “a current through a superconducting wire will never dissipate,”  as in  choice (D) . As for  (A) , the passage states that an even number of fermions (which, according to the first paragraph,  “include electrons, protons, and neutrons” ) constitute a boson, but not an odd number (1⁄2 integer times an odd will not give an integer). The last paragraph states that  “scientists argue for the existence of skyrmions”  in a medium that might permit them to be formed, implying that they have not yet been discovered, so eliminate  (B) . In  (C) , the author states that two electrons cannot circle a nucleus in the same orbit, but they could spin in different orbits that are the same distance from the nucleus. Finally, in  (E) , the author gives two examples of fermions becoming bosons at cooled temperatures but does not say this is the only situation in which this can occur.

Answer: D

Sajjad1994 · Answer

OE

5. According to the passage, which of the following describes a difference between fermions and bosons?

The first paragraph states that fermions obey the Pauli principle, according to which no two particles can occupy the same fundamental state. The second paragraph states that bosons tend to bunch together in exactly the same state. This supports choice (A) and is the opposite of (E); thus, (E) is incorrect. Choice (D) is also the opposite of what the passage claims. Bosons have integral spin values and fermions have “half-integral” spin. Answer (B) is incorrect because the passage does not discuss the total number of particle types for bosons or fermions, and answer (C) is incorrect because the passage explicitly states that both fermions and bosons can exist in groups.

Answer: A

Sajjad1994 · Answer

OE

6. Based on the information in the passage about the Pauli exclusion principle, to which one of the following situations would this principle be most relevant?

The passage states that the Pauli principle prohibits any two particles from inhabiting the same fundamental state. Further, the Pauli principle should be applied to fermions,  “which include electrons, protons, and neutrons,”  but not bosons (from the second paragraph). Answer  choice (A)  discusses electrons, which are fermions, avoiding occupation of identical energy levels, so  (A)  is relevant and thus the correct answer. As for  (B) , a charged particle in a magnetic field neither provides the criteria for a fermion nor references inhabitance of the same state. Answer  (C)  does not specify the type of particle.  Answer (D)  is about photons, which are described in the passage as bosons, to which the Pauli principle does not apply. Regarding  (E) , the passage explicitly states that the Higgs particle is a boson, so the Pauli exclusion principle doesn’t apply here. 
  
  Answer: A

Subatomic particles can be divided into two classes: fermions and boso

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