Ionising Radiation

If you multiply your distance from the source by “r”, then your exposure is multiplied by 1/r² (that is, decreased).

The half-life of a particular radionuclide is the time it takes for half of the remaining atoms of that particular radionuclide to decay. Choice B is not the same thing.

The radioactive sources are loaded into their applicators automatically and remotely when staff have left the room. They are automatically retrieved and returned to a shielded safe when staff enter the room.

Every object emits infrared rays in proportion to its temperature. IR rays have too little energy to ionise the medium that they strike.

X-rays are ionising radiation. This means that ions may be formed from the atoms that make up DNA. In this case, the chemical bonds between atoms will be broken, and the molecule will be changed.

Gamma rays and x-rays are indistinguishable, once they have travelled away from their site of production. So a 140 keV gamma or x-ray is more penetrating than a lower energy one.

This dose given acutely to the entire body will probably be lethal. Higher doses can be withstood if only a limited part of the body is exposed or if the dose is accumulated over a long time.

It is the ability to image internal structures without having them partially obscured by the tissue on either side as is the case for “conventional” radiography that makes CT such a useful diagnostic tool. (Also there is no need to cut the person open to see what is inside!)

If most gamma photons emerge from the body, the maximum amount of information will be available, and the minimum amount of radiation dose will be deposited in the patient.

100 mSv/5 years is the permitted dose to workers who because they are employed derive the benefits of employment which outweighs the small theoretical detriment they suffer due to their exposure.