TOPIC 26 RADIOACTIVITY

Which type of radiation consists of electrons?

• alpha-particles

• beta-particles

• gamma-rays

• X-rays

A sample of a radioactive isotope produces a count rate of 10 000 counts per minute. The half-life of the isotope is one day.

What was the count rate of the sample two days ago?

• 2500 counts per minute

• 5000 counts per minute

• 20 000 counts per minute

• 40 000 counts per minute

• A

• B

• C

• D

Which states the three types of radiation emitted by radioactive isotopes in order of their ionising effect from highest to lowest?

• alpha-particles, beta-particles, gamma-rays

• alpha-particles, gamma-rays, beta-particles

• beta-particles, gamma-rays, alpha-particles

• gamma-rays, beta-particles, alpha-particles

Which statement about the half-life of a radioactive isotope is correct?

• Half-life changes as the isotope decays.

• Half-life is the time it takes for the nucleon number of the isotope to halve.

• Half-life is half the time it takes for the number of nuclei of the isotope to decrease to zero.

• Half-life is the time it takes for the number of nuclei of the isotope to decrease by half.

A factory continuously produces plastic sheets. A radioactive isotope and a detector are used to check the thickness of the sheets.

What is the most suitable source to use?

• an alpha source with a half-life of a few minutes

• an alpha source with a half-life of several years

• a beta source with a half-life of a few minutes

• a beta source with a half-life of several years

A source contains a radioactive material.

Without the radioactive source present, a detector records a background count rate of 20 counts per minute.

This source is placed in a fixed position near the detector. Initially a count rate of 520 per minute is recorded.

What count rate is recorded after a time of two half-lifes of the radioactive source?

• 125 counts per minute

• 130 counts per minute

• 135 counts per minute

• 145 counts per minute

• A

• B

• C

• D

The half-life of a radioactive isotope is 24 hours. A sample of this isotope produces an initial count rate of 720 counts per second.

How long does it take for the count rate to fall to 90 counts per second?

• 3 hours

• 72 hours

• 96 hours

• 192 hours

Which type of electromagnetic radiation is produced during radioactive decay?

• alpha-particles

• beta-particles

• gamma-rays

• X-rays