Week 3

Question 1

Man-made exposure contributes how much of the total annual exposure from all sources?

Answer 1

about 14%

Question 2

exposure -

Answer 2

Traditional method of measuring the amount of ionisation: ratio of the total charge produced (of one sign, usually electrons) in a small volume of air;

unit of exposure for air is Coulombs per kilogram of air (C/kg) but it has largely been replaced by Röntgen ( 1R = 2.58 × 10−4 C/kg);

Question 3

what exposure applies to?

Answer 3

only X- and gamma rays (photons)

Question 4

measure of radiation damage -

Answer 4

absorbed dose

Question 5

absorbed dose unit

Answer 5

Gray (Gy) - equivalent to the absorption of one joule of energy in a kilogram of a substance by ionising radiation

Microgray (μGy) is one millionth of a Gray (1x10⁻⁶)
Milligray (mGy) is one-thousandth of a Gray (1×10⁻³)

Question 6

KERMA -

Answer 6

Kinetic Energy Released in Medium;

When a photon beam interacts with a medium, the photon interactions release electrons with Kinetic energy into the medium;

Question 7

KERMA vs absorbed dose:

Answer 7

KERMA is energy released, and absorbed dose is energy absorbed;

@ high energies (up to 1 MeV) - different

@ low energies - roughly equal