Please enable JavaScript.
Coggle requires JavaScript to display documents.
Physics P4 - Coggle Diagram
Physics P4
-
Ionising radiation
Beta particles are high-speed electrons - an electron, moderately ionising, moderately penetrating and ca travel a few meters
Gamma rays are EM waves with a short wavelength - weakly ionising, penetrate far into materials, travel long distances.
Alpha particles are helium nuclei - 2 neutrons and 2 protons, highly ionising, can't travel far and can't penetrate very far
Half life
Radioactive decay is entirely random so you can't predict which nucleus will decay next or when a nucleus will decay.
The half-life is the time taken for the number of radioactive nuclei in an isotope to halve. (measured in Becquerels)
Radiation can be measured with a Geiger-Muller tube and counter which records the count rate - the number of radiation counts reaching it per second
Background radiation
The radiation dose tells you the risk of harm to body tissues due to exposure to radiation. It's measure in sieverts (Sv).
Irradiation
Exposure to radiation is called Irradiation. Keeping sources in lead-lined boxes, standing behind barriers or being in a different room and using remote controlled arms when working with radioactive sources are all ways of reducing irradiation.
Background radiation is the low-level radiation that's around us all the time. It comes from: naturally occurring isotopes, space (cosmic rays) and human activity.
-
Isotopes
Isotopes of an element are atoms with the same number of protons (the same atomic number, and so the same charge on the nucleus) but a different number of neutrons (a different mass number).
Unstable isotopes tend to decay into other elements and give out radiation as they try to become more stable. This process is called radioactive decay.
Contamination
Contamination is radioactive particles getting onto objects. Contamination is especially dangerous because radioactive particles could get inside your body. Gloves and tongs should be used when handling sources, to avoid particles sticking to your skin or under your nails, some industrial workers wear protective suits to stop them breathing in particles.
Exposure to some sources can be more harmful than to others. Outside the body, beta and gamma are the most dangerous but inside the body alpha is the most dangerous.
Nuclear Equation
Mass and atomic numbers have to balance. Alpha decay decreases the charge and the mass of the nucleus. Beta decay increases the charge of the nucleus. Gamma rays don't change the charge or mass of the nucleus.