Question 1

Which of the following statements best explains why the mass of a stable nucleus is less than the sum of the masses of its individual protons and neutrons?

Accepted Answer

Some of the mass is converted into binding energy, which holds the nucleus together, according to $$E = mc^2$.

Question 2

A nuclide is represented as $$^{A}_{Z}X. If an $$atom of $$^{238}_{92}U$$ undergoes alpha decay, what is the resulting daughter nuclide?

Accepted Answer

$$^{234}_{90}Th$$

Question 3

Which of the following best describes the process of beta-minus decay?

Accepted Answer

A neutron in the nucleus transforms into a proton, emitting an electron and an antineutrino.

Question 4

Which of the following conservation laws is NOT violated in any type of radioactive decay?

Accepted Answer

Conservation of nucleon number

Question 5

A radioactive sample contains $$N_0$$ nuclei at time $$t=0. If $$the decay constant is $$\lambda$$, what is the number of undecayed nuclei at time $$t$$?

Accepted Answer

$$N = N_0$ e$$^{-\lambda t}$$

Question 6

Which type of radiation is most likely to be stopped by a few centimeters of lead?

Accepted Answer

Gamma rays

Question 7

A sample of carbon-14 has a half-life of 5730 years. If a sample originally contains $$1.0 mg of $$carbon-14, how much remains after $$11,460$$ years?

Accepted Answer

$$0.25 mg$$

Question 8

Which device is best suited for detecting the tracks of charged particles by forming droplets along their paths in a supercooled gas?

Accepted Answer

Cloud chamber

Question 9

Why are extra neutrons required for the stability of heavy nuclei (high-Z elements)?

Accepted Answer

They help offset the Coulomb repulsion between protons by increasing the strong nuclear force without adding more repulsive charge.

Question 10

Which of the following statements about radioactive decay is correct?

Accepted Answer

The decay of each nucleus is a random process and is not influenced by the decay of other nuclei.

Question 11

Which of the following best describes the role of the weak nuclear force in radioactive decay?

Accepted Answer

It is responsible for beta decay processes in nuclei.

Question 12

A nucleus emits a gamma ray. Which of the following changes occur as a result?

Accepted Answer

The nucleus transitions from an excited state to a lower energy state without changing its atomic or mass number.

Question 13

Which of the following is a real-world application of alpha radiation?

Accepted Answer

Smoke detectors, where alpha particles ionize air and the presence of smoke interrupts the current.

Question 14

If a radioactive isotope decays through a series of alpha and beta decays, what is the general effect on its position in the periodic table?

Accepted Answer

Alpha decay decreases atomic number by 2; beta-minus decay increases atomic number by 1.

Question 15

Which of the following best explains why carbon-14 dating is not reliable for objects older than about 60,000 years?

Accepted Answer

Too little carbon-14 remains to be accurately measured.

Question 16

Which of the following equations correctly relates the half-life $$t_{1/2} to $$the decay constant $$\lambda$$?

Accepted Answer

$$t_{1/2} = \frac{\ln 2}{\lambda}$$

Question 17

Which of the following best describes quantum tunneling in the context of alpha decay?

Accepted Answer

The alpha particle escapes the nucleus by passing through an energy barrier it classically could not surmount.

Question 18

A Geiger counter detects radiation by which of the following mechanisms?

Accepted Answer

Ionization of gas inside a tube, leading to a cascade of ions collected as an electrical pulse.

Question 19

Which of the following is true about the binding energy per nucleon for stable nuclei?

Accepted Answer

It is higher for more stable nuclei, indicating stronger binding.

Question 20

Which of the following statements about neutrinos in beta decay is correct?

Accepted Answer

Neutrinos are emitted to conserve energy and momentum in beta decay.

Chpt 30

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