Nuclear and Particle Physics

Physics · 11th Class (Intermediate Part 1) · BISE Lahore

70 questions

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Nuclear and Particle Physics Test

10 questions · Nuclear and Particle Physics × 10

Sample questions

Showing 20 of 70 questions from this chapter. The full bank is in the chapter test below.

1
Which one of the following is a fundamental particle?
- A.Electron (correct answer)
- B.Proton
- C.Neutron
- D.Alpha particle
Why: The electron is a lepton and shows no internal structure. A proton and a neutron are each built from three quarks, and an alpha particle is a bound state of two protons and two neutrons.
2
A particle and its anti-particle have
- A.the same mass and the same charge
- B.the same mass but opposite charges (correct answer)
- C.different masses and opposite charges
- D.no mass at all
Why: The Standard Model gives every particle an anti-particle of exactly the same mass but opposite electric charge and magnetic moment. The positron, for example, has the mass of an electron but a charge of $+e$ .
3
The first anti-particle to be discovered experimentally was the
- A.anti-proton
- B.anti-neutrino
- C.positron (correct answer)
- D.anti-neutron
Why: C. D. Anderson discovered the positron in a cloud-chamber photograph of cosmic rays in 1932. The anti-proton was not found until 1955, when accelerators could reach high enough energies.
4
The particles inside the nucleus that are together called nucleons are
- A.electrons and protons
- B.protons and neutrinos
- C.neutrons and electrons
- D.protons and neutrons (correct answer)
Why: The nucleus is built from protons (Z of them) and neutrons (N of them). Electrons are not nuclear particles, although beta decay can create one inside the nucleus.
5
The neutron was discovered in 1932 by
- A.Ernest Rutherford
- B.James Chadwick (correct answer)
- C.J. J. Thomson
- D.Niels Bohr
Why: James Chadwick identified the neutral particle ejected from beryllium under alpha bombardment in 1932 and named it the neutron.
6
If a nucleus contains $Z$ protons and $N$ neutrons, its mass number $A$ is given by
- A. $A = Z$
- B. $A = Z - N$
- C. $A = N + Z$ (correct answer)
- D. $A = N$
Why: The mass number counts every nucleon in the nucleus, so $A = N + Z$ . The number of protons alone is the atomic number $Z$ .
7
Two nuclides are isotopes of the same element. They have
- A.the same number of neutrons but different numbers of protons
- B.the same mass number but different atomic numbers
- C.equal numbers of protons and neutrons each
- D.the same number of protons but different numbers of neutrons (correct answer)
Why: Isotopes have the same atomic number $Z$ but different neutron numbers $N$ , so their mass numbers differ. Carbon-12 and carbon-14 are examples.
8
A nuclide contains 87 nucleons and 50 neutrons. The element is
- A.rubidium ( $Z = 37$ ) (correct answer)
- B.krypton ( $Z = 36$ )
- C.strontium ( $Z = 38$ )
- D.yttrium ( $Z = 39$ )
Why: $Z = A - N = 87 - 50 = 37$ , and the element with atomic number 37 is rubidium.
9
The unified atomic mass unit ( $1\ \mathrm{u}$ ) is defined as
- A.the mass of one hydrogen atom
- B.one-twelfth of the mass of a carbon-12 atom (correct answer)
- C.the average mass of a proton and a neutron
- D.the mass of one electron
Why: $1\ \mathrm{u}$ is exactly one-twelfth of the mass of a carbon-12 atom, which equals $1.66 \times 10^{-27}\ \mathrm{kg}$ .
10
The energy equivalent of a mass of $1\ \mathrm{u}$ is about
- A. $9.1\ \mathrm{MeV}$
- B. $1.02\ \mathrm{MeV}$
- C. $931\ \mathrm{MeV}$ (correct answer)
- D. $0.51\ \mathrm{MeV}$
Why: Using $E = mc^2$ , a mass of $1.66 \times 10^{-27}\ \mathrm{kg}$ corresponds to an energy of about $931\ \mathrm{MeV}$ . The value $1.02\ \mathrm{MeV}$ is the rest energy of an electron-positron pair, not of one atomic mass unit.
11
The rest mass of an electron is $0.00055\ \mathrm{u}$ . Its rest energy is about
- A. $0.09\ \mathrm{MeV}$
- B. $5.1\ \mathrm{MeV}$
- C. $1.02\ \mathrm{MeV}$
- D. $0.51\ \mathrm{MeV}$ (correct answer)
Why: $E = mc^2 = 0.00055 \times 931\ \mathrm{MeV}$ , which is about $0.51\ \mathrm{MeV}$ ; twice this value, $1.02\ \mathrm{MeV}$ , is the rest energy of an electron-positron pair.
12
Which of the four fundamental forces of nature is the strongest?
- A.Gravitational force
- B.Strong nuclear force (correct answer)
- C.Electromagnetic force
- D.Weak nuclear force
Why: Taking the strong nuclear force as 1, the electromagnetic force is about $10^{-2}$ , the weak nuclear force about $10^{-19}$ and gravity only about $10^{-30}$ .
13
Which fundamental force has a negligible effect between individual elementary particles?
- A.Strong nuclear force
- B.Weak nuclear force
- C.Gravitational force (correct answer)
- D.Electromagnetic force
Why: Gravity is the weakest of the four forces and becomes significant only when very large masses are involved, so between individual particles its effect is negligible.
14
Radioactive beta decay is caused by
- A.the strong nuclear force
- B.the electromagnetic force
- C.gravity
- D.the weak nuclear force (correct answer)
Why: The weak nuclear force is the only force that can change the identity of a particle, which is exactly what happens when a neutron turns into a proton during beta decay.
15
The strong nuclear force acts between
- A.all pairs of nucleons: proton-proton, neutron-neutron and proton-neutron (correct answer)
- B.protons only
- C.neutrons only
- D.a proton and a neutron only
Why: The strong force is charge independent and attracts every pair of nucleons within about $10^{-15}\ \mathrm{m}$ . This is what holds the nucleus together against the electrostatic repulsion of the protons.
16
The electromagnetic force between two charged particles is transmitted by the exchange of
- A.gluons
- B.photons (correct answer)
- C.W and Z bosons
- D.gravitons
Why: Electromagnetic interactions are carried by photons, the quanta of the electromagnetic field, which are exchanged between charged particles.
17
The strong force between quarks is carried by
- A.photons
- B.gravitons
- C.gluons (correct answer)
- D.W bosons
Why: Gluons are the exchange particles of the strong force. Photons carry the electromagnetic force, while the W and Z bosons carry the weak force.
18
Which statement about an alpha particle is correct?
- A.It is a helium nucleus containing two protons and two neutrons (correct answer)
- B.It is a single proton
- C.It is a fast-moving electron
- D.It is an electron-positron pair
Why: An alpha particle is a helium-4 nucleus containing two protons and two neutrons, so it carries a charge of $+2e$ and has a mass of about $4\ \mathrm{u}$ .
19
The charge on an alpha particle is
- A. $-3.2 \times 10^{-19}\ \mathrm{C}$
- B. $+3.2 \times 10^{-19}\ \mathrm{C}$ (correct answer)
- C. $+1.6 \times 10^{-19}\ \mathrm{C}$
- D.zero
Why: The two protons give a charge of $2 \times 1.6 \times 10^{-19}\ \mathrm{C} = 3.2 \times 10^{-19}\ \mathrm{C}$ , and the two neutrons are electrically neutral.
20
When a nucleus emits an alpha particle, its mass number and atomic number change as follows:
- A. $A$ falls by 2 and $Z$ falls by 4
- B. $A$ falls by 4 and $Z$ falls by 4
- C. $A$ falls by 4 and $Z$ falls by 2 (correct answer)
- D. $A$ is unchanged and $Z$ falls by 2
Why: The emitted alpha particle takes away two protons and two neutrons, so the daughter nucleus has a mass number smaller by 4 and an atomic number smaller by 2.

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