MCQs – Radioactive Decay (set 2)

Each of the nuclei below is accelerated from rest through the same potential difference. Which one completes the acceleration with the lowest speed?

The graph of neutron number against proton number presents a sequence of radioactive decays. Nucleus X is at the start of the sequence and, after the decays have occurred, nucleus Y is formed. What is emitted during the sequence of decays?

• one α-particle followed by one β-particle

• one α-particle followed by two β-particles

• two α-particles followed by two β-particles

• two α-particles followed by one β-particle

What is a reasonable estimate of the diameter of an alpha particle?

• 10^-15 m

• 10^-12 m

• 10^-9 m

• 10^-6 m

A freshly prepared radioactive source of half-life 2.0 h emits radiation of intensity 64× the permissible safe level. The minimum time after which it would be possible to work safely with this source is:

• 12 h

• 24 h

• 64 h

• 128 h

What could the scatter of points about the best-fit curve represent for actual radioactive decay?

• A background count not being taken into account

• more than one type of radiation being present

• the random nature of radioactive decay

• the spontaneous of radioactive decay

During β⁻ decay…

• an atomic electron is ejected.

• an electron that is already present within the nucleus is ejected.

• a neutron in the nucleus decays emitting an electron.

• a part of the binding energy of the nucleus is converted into an electron.

After 280 days, the activity of a radioactive sample is 6000s⁻¹ (counts per second). The activity reduces to 3000 s⁻¹ after a further 140 days. What is the initial activity of the sample?

• 3000 s⁻¹

• 6000 s⁻¹

• 9000 s⁻¹

• 24 000 s⁻¹

A nucleus with atomic number Z = 78 and nucleon number A = 214 emits the following in a sequence β⁻, β⁻, α, β⁻, β⁻, α. The resulting nucleus X may be written as

A nickel nucleus ⁵⁹₂₈Ni can be transformed by a process called electron-capture. In this process, the nucleus absorbs an orbital electron. If no other process is involved, what is the resulting nucleus?

The ionising properties of radiations determine their penetrating power. Which of the following statements is correct?

• α-particles are not very ionising so they are stopped by thin paper.

• α-particles are very ionising so can only travel a few centimetres in air.

• γ-radiation is very penetrating because it is very ionising.

• γ-radiation is not very penetrating because it is very ionising.