Lecture 4 Flashcards
What are the units for Radioactivity
curie or bequerel
Units of absorbed dose
rad and gray
Units of Equivalent dose
rem or sievert
Unit of radiation exposure
roentgen
What is absorbed dose
a mesure of the energy deposited in joules/kg by the radiation in the material that absorbs it
For what types of radiation is the damage caused to biological tissue proportional to energy deposited and for one/s that it isn’t, why
Proportional - X-rays, gamma, electrons (Beta)
Not - Alpha, because its ionising energy decreases with distance from the source
What is equivalent dose and what is the unit
the absorbed dose adjusted for the different biological effects of different types of radiation
sievert
What is effective dose
an estimate of the overall risk of of harm due to exposure due to ionising radiation, taking into account absorbed dose, type of radiation and the sensitivity of the organs and tissues to radiation-induced damage
What are the 2 types of harmful effects of radiation
- Deterministic effects - have a threshold dose above which frequency and severity of the effect increases with increasing dose
- Stochastic effects - have a proportional relationship between dose and probability of occurrence (meaning effects can never be eliminated only minimised, e.g. cancer)
How many Gy/Sievert before you will definitely die
8 (>7)
What is radiation hormesis
The debated benificaial effect of low doses of radiation on health
What does ionising radiation actually do to tissue
The tissue absorbs it and it causes massive, non-specific disorganisation or injury of biological cells and tissues
What is the process of indirect damage
Water molecules are damaged releasing an OH free radical, the free radicals react with DNA and damage it
What is the process of direct damage
DNA molecules are struck by radiation, ionized, resulting in damage
Where does radon come from
It is thought to escape from voids in igneous rocks which contain Uranium - due to the crystalline structure
