Exploring Radioactivity and Its Effects

Which of the following is NOT a type of radioactive decay?

• Alpha decay

• Beta decay

• Gamma decay

• Delta decay

Answer explanation

Delta decay is not a recognized type of radioactive decay. The main types are alpha decay, beta decay, and gamma decay, which involve the emission of particles or energy from unstable nuclei.

What is meant by the half-life of a radioactive isotope?

• The time it takes for all the atoms to decay

• The time it takes for half the atoms to decay

• The time it takes for the isotope to become stable

• The time it takes for the isotope to double in mass

Answer explanation

The half-life of a radioactive isotope is defined as the time it takes for half of the atoms in a sample to decay. This means that after one half-life, 50% of the original atoms remain, making this the correct choice.

Which of the following is a common application of radioactivity in medicine?

• X-ray imaging

• MRI scanning

• Radiotherapy for cancer treatment

• Ultrasound scanning

Answer explanation

Radiotherapy for cancer treatment is a common application of radioactivity in medicine, using radioactive substances to target and destroy cancer cells, unlike X-rays, MRI, and ultrasound which do not involve radioactivity.

Which type of radiation is the most penetrating and can pass through several centimetres of lead?

• Alpha particles

• Beta particles

• Gamma rays

• Neutrons

Answer explanation

Gamma rays are the most penetrating type of radiation, capable of passing through several centimeters of lead due to their high energy and lack of charge, unlike alpha and beta particles which are less penetrating.

What is a possible health effect of exposure to high levels of ionising radiation?

• Improved eyesight

• Hair growth

• Increased risk of cancer

• Stronger bones

Answer explanation

Exposure to high levels of ionising radiation can damage DNA and cells, leading to mutations. This increases the risk of developing cancer, making 'Increased risk of cancer' the correct choice. The other options are not valid health effects.

Which equation correctly represents the half-life calculation for a radioactive substance?

Answer explanation

The correct equation for half-life is \(N = N_0 \times \left(\frac{1}{2}\right)^{\frac{t}{T_{1/2}}}\). This formula shows how the quantity of a radioactive substance decreases over time, halving every half-life period.

Which of the following is a difference between nuclear fission and nuclear fusion?

• Fission combines small nuclei, fusion splits large nuclei

• Fission occurs in the Sun, fusion occurs in nuclear power stations

• Fission splits large nuclei, fusion combines small nuclei

• Both processes release no energy

Answer explanation

The correct choice is that fission splits large nuclei while fusion combines small nuclei. Fission occurs in nuclear power plants, and fusion occurs in stars like the Sun, both releasing energy.

Which radioactive isotope is commonly used in smoke detectors?

• Carbon-14

• Uranium-235

• Americium-241

• Iodine-131

Answer explanation

Americium-241 is the radioactive isotope used in smoke detectors. It emits alpha particles, which ionize the air in the detector, allowing it to sense smoke effectively. The other isotopes listed are not used for this purpose.

What is the main source of background radiation in the United Kingdom?

• Cosmic rays from space

• Medical X-rays

• Radon gas from the ground

• Nuclear power stations

Answer explanation

The main source of background radiation in the UK is radon gas from the ground, which seeps into buildings and contributes significantly to overall exposure, more than cosmic rays, medical X-rays, or nuclear power stations.

Which of the following best describes the process of nuclear fusion?

• A large nucleus splits into two smaller nuclei, releasing energy

• Two small nuclei combine to form a larger nucleus, releasing energy

• An atom loses electrons to become an ion

• A neutron is absorbed by a nucleus without any energy release

Answer explanation

Nuclear fusion occurs when two small nuclei combine to form a larger nucleus, releasing energy in the process. This is the opposite of nuclear fission, where a large nucleus splits into smaller ones.