Nuclear Physics and Ionizing Radiation Principles

Ionization and Atomic Structure

1.

• a) B
• b) Draw
• c) Energy is transferred to the kinetic energy stored in an electron, causing electrons to be lost, so turning the initial atom into an ion.

Radioactive Count Rate Analysis

2.

• a) [No data provided]
• b) [No data provided]
• c) The trend in the change in count rate from the previous column is decreasing.
• d)
  1. Repeat the experiment more times and find the average.
  2. Use more cards.
• e) One way the student could test whether alpha particles were emitted from the source is by increasing the distance between the source and the detector, as the count rate will be lower if alpha particles were emitted.

Nuclear Energy and Medical Applications

3.

• a) Advantage: Does not produce carbon dioxide when functioning. Disadvantage: Highly dangerous if a problem occurred (i.e., damaged).
• b) The moderator helps slow down the neutrons so they can collide with the other atoms nearby.
• c)
  1. In a PET scanner, a radioactive tracer is injected into the body. The tracer releases positrons. When a positron meets an electron in the body, they annihilate each other and their mass is converted into energy, producing gamma rays that travel in opposite directions.
  2. The source must be nearby because positrons only travel a very short distance before colliding with electrons and annihilating.
• d) ¼ (1,0) n

Half-Life Calculations

4)

a) 0.5 / 2 = 0.25; 0.25 / 2 = 0.125; 12 / 2 = 6 | Answer: 6 hours

b) 0.5^3 = 0.125

Atomic Decay Processes

5)

• a) C (T)
• b) C (V)
• c) W
• d) The neutron of atom Q has become a proton and an electron.

Radiation Safety and Biological Effects

6)

Ionizing radiation can damage cells and DNA, which can cause mutations and may lead to cancer.

Alpha radiation is very strongly ionizing but cannot travel far and can be stopped by paper or skin. However, it is very dangerous if it enters the body through breathing in or swallowing radioactive substances. Inside the body, it can damage nearby cells and tissues. For example, Alexander Litvinenko was poisoned with a substance which gives off alpha radiation. People around him in the café were not affected because alpha radiation cannot travel far, but it was very harmful inside his body.

Gamma radiation is less ionizing but very penetrating, so it can pass through the body and damage cells deep inside. In hospitals, gamma radiation is used for medical imaging. Doctors prepare the patient and then leave the room and close the door before the imaging starts. This increases the distance from the radiation source and reduces the amount of radiation they are exposed to.

Other safety precautions include limiting the time spent near the radiation source and using shielding such as thick lead or concrete to absorb the radiation.