P3 Topic 3 - Radioactivity and Ionising Radiation Flashcards
What is neutron radiation?
Neutrons are more penetrating than alpha, beta and gamma. Absorbing a neutron can make an atoms radioactive, causing them to decay, so neutrons can be called ‘indirectly ionising’.
What is positron emission?
Positrons are positively charged beta radiation. It is the antiparticle of the electron. They have the same properties as beta radiation, so they are light and fast moving, moderately ionising and are stopped by a thin sheet of metal. If a positron collides with an electron they annihilate each other.
When does beta-minus decay occur, in terms of the number of neutrons in an atom?
Beta minus decay occurs when atom is neutron rich. For every beta particle ejected by the atom, a neutron turns into a proton. The mass number stays the stays but the atomic number increases by one.
When does beta-plus decay occur, in terms of the number of neutrons in an atom?
Beta plus decay occurs when atom is neutron deficient. For every beta particle ejected by the atom, a proton turns into a neutron. The mass number stays the stays but the atomic number decreases by one.
When does alpha decay occur in an atom?
Atoms with more than 82 protons, such as uranium and radium, give off 2 neutrons and 2 protons (a helium nucleus). The mass number decreases by 4 while the atomic number decreases by 2.
When is gamma radiation emitted from atoms?
Atoms give off gamma radiation when the have too much energy, although atoms never give off just gamma and would also emit alpha or beta radiation as well. Gamma emissions do not affect the mass or atomic number.
What are the following particles made of:
- Protons
- Neutrons
- Two up quarks and one down quark
2. Two down quarks and one up quark
How are tracers used in medicine?
Some radioactive isotopes are used as tracers to diagnose some medical conditions. The tracer is injected into the patient and a radiation detector monitors the tracer as it travels around the body to find the location where it is strongest. These tracers should give off beta or gamma only as they are the most penetrating and least ionising. They should also have short half-lives so that patients don’t remain radioactive after the procedure.
How do PET scans help diagnose illnesses?
- A patient is injected with a substance attached to a radioactive isotope, e.g. Glucose with carbon-11, for example. Over an hour, the tracer travels around the body to the organs.
- Positrons are emitted by the isotope which collide and create gamma rays. The glucose is more concentrated at cells which are respiring more.
- The PET scanner then detects the gamma rays and uses this information to pinpoint the point of origin, allowing doctors to find cancer cells, which tend to use up more glucose than most other cells.
How can radiation cause tissue damage and mutations?
Ionisation can affect the DNA in a cell, preventing it from functioning properly, potentially damaging or killing it. On the other hand, it can also cause the cell(s) to divide uncontrollably into a cancer.
In hospitals, patients are exposed to as little radiation as possible to reduce the risk of developing cancer. Medical staff also try to decrease their exposure to radiation by controlling equipment using radiation from a distance or behind lead screens.
How can radiation be used to treat tumours?
Internally:
Radioactive material placed inside body near or inside tumour. Ionisation kills of the cancer as well as a few neighbouring cells.
Externally:
X-rays or gamma rays are aimed at the tumour from different angles so that the cancerous region is affected the most and dies.
State some social and ethical issues of using radiation in medical physics.
Always damages some healthy cells
Person may develop a second cancer
Doesn’t always work
Side effects may occur months or years afterwards
