Fisika Nuklir

Nuclear particles and nuclear radiation may cause ionisation as they pass through matter. Which of the following is the most ionising?

• α particles

• β particles

• γ rays

• neutrons

An unstable nucleus recoils as it emits an alpha particle. This is due to the conservation of

• charge.

• kinetic energy.

• momentum.

• total energy.

The table below gives the range and number of ion pairs per centimetre produced by β particles, compared to α particles of the same energy. Select the row from the table which shows the correct comparison.

• Range of β particles: greater, Number of ion pairs per centimetre: greater

• Range of β particles: smaller, Number of ion pairs per centimetre: greater

• Range of β particles: greater, Number of ion pairs per centimetre: smaller

• Range of β particles: smaller, Number of ion pairs per centimetre: smaller

Radioactive decay is said to be a spontaneous process. This means that:

• we cannot know when a nucleus will decay.

• we cannot know which nucleus will decay next.

• we cannot know how many nuclei will decay.

• we cannot influence when a nucleus will decay.

Tags

NGSS.HS-PS1-8

In an experiment to measure the activity of a radioactive source the measured activity should always be corrected by:

• adding the background count.

• adding the background count rate.

• subtracting the background count.

• subtracting the background count rate.

When measuring the count rate from a radioactive source it is usual to also measure the background count rate. The background count rate must be:

• as large as possible for an accurate experiment.

• measured when the source is in place.

• recorded for the same time as the count rate.

• subtracted from the count rate measured from the source.

Before carrying out an experiment to measure the activity from a radioactive source, it is usual to measure the background count. The background count obtained is not affected by the

• location of the experiment.

• temperature of the surroundings.

• time interval used for the count.

• type of detector being used.

Health and safety guidelines state that radioactive sources suitable for school experiments should only be handled using long tongs, and only for restricted periods of time. Select the row in the table that gives the type of radiation that is most dangerous to the human body, in these circumstances, with the correct reason.

• α-radiation because it is the most ionising.

• α-radiation because it is the most massive.

• β-radiation because it can penetrate up to a metre of air.

• β-radiation because it can penetrate the skin and enter the body.

Some rocks contain lead as a result of radioactive decay. In one such decay a fixed amount of polonium decays to a stable isotope of lead. Which graph correctly shows the variation with time of the number of lead atoms, N, produced from the decay of polonium in the rock?

• A

• B

• C

• D

Tags

NGSS.HS-PS1-8

Which one of the following does not contribute to background radiation?

• Dead matter

• Living matter

• Mobile phones

• Rocks