Radioactive decay

. Radioactive materials decay naturally and release alpha, beta or gamma radiation. What is the name given to the number of nuclei that decay each second?

• •

  •The rate of changing nucleuse

• •

  •The half-life

  •

• •

  •The activity

What is a becquerel?

• •One decay per second

• •One decay per minute

• •One decay per hour

What is the half-life of a radioactive isotope?

• •The time taken for the daughter nuclei to increase

• •The time taken for the nucleus to decay

• •The time taken for half the parent nuclei to decay

•Which of the following radioactive isotopes would be most suitable as a tracer to monitor blood flow in a patient’s heart?

• •Americium-237 emits alpha particles and has a half-life of 78 minutes

• •Technetium-99m emits gamma waves and has a half-life of 6 hours

• •Krypton-78 emits beta particles and has a half-life of 10.7 years

A radioactive source’s activity falls from 8,000 counts per minute to 500 counts per minute in 20 hours. What is the half-life of the source?

• •5 hours

• •10 hours

• •30 minutes

Which of the following isotopes would be used in a machine for measuring paper thickness?

• •An alpha source with a short half-life

• •A beta source with a long half-life

• •A gamma source with a long half-life

What percentage of an original polonium sample will remain after three half-lives have passed?

• •6.25%

• •12.5%

• •25%

Wood from a sample of carbon-14 in a living tree has an activity of 120 Bq. Wood found in an archaeological dig has an activity of 30 Bq. The half-life of carbon-14 is 5,730 years. Estimate the age of the dead wood

• •17,190 years

• •11,460 years

• •5,730 years

An internal cancer is treated by injecting a small quantity of a radioactive isotope directly into the cancer. What isotope should be used?

• •An alpha emitter with a short half-life

• •A beta emitter with a short half-life

• •A gamma emitter with a short half-life

In a cereal factory the filling of cereal into a cardboard box is measured with a radioactive source that is placed just below the top. When the cereal reaches it, the count rate at the other side is significantly reduced, stopping the filling process. What should the radioactive source be?

• •A gamma source with a short half-life

• •A beta source with a long half-life

• •An alpha source with a short half-life