Radioactivity：練習題

Which type of radiation has the highest ionizing power but the lowest penetrating power?

A radioactive source has an initial activity of \(800\text{ Bq}\). If the half-life of the source is \(10\) minutes, what will its activity be after \(30\) minutes?

A radioactive sample of an isotope has an activity of \( 4800 \text{ Bq} \). After a period of \( 12 \text{ hours} \), its activity is found to be \( 300 \text{ Bq} \). If the background radiation is constant at \( 20 \text{ Bq} \) throughout the measurement, calculate the half-life of this isotope.

An isotope of Carbon is represented by the notation \(^{14}_{6}\text{C}\). How many neutrons are present in the nucleus of this atom?

A radioactive isotope has a half-life of \(4\text{ hours}\). If a sample initially contains \(1.2 \times 10^{20}\) undecayed nuclei, how many undecayed nuclei will remain in the sample after \(12\text{ hours}\)?

A radioactive sample has an initial activity of \( 800 \text{ Bq} \). If the half-life of the sample is \( 10 \text{ minutes} \), calculate its activity after \( 30 \text{ minutes} \).

A neutral atom of an isotope is represented by the nuclide notation \( {}^{235}_{92}\text{U} \). State the number of neutrons and electrons present in this atom.

A sample of a radioactive isotope is used in a laboratory experiment. The initial activity of the sample is measured to be 800 Bq. After a period of 12 hours, the activity is found to have decreased to 100 Bq.

(a) Determine the half-life of this radioactive isotope.
(b) Calculate the activity of the sample after a total of 20 hours have passed since the initial measurement.
(c) State whether radioactive decay is a predictable process for a single nucleus and explain your answer using the terms random and spontaneous.