Radiation and Illumination Flashcards
Ionising Radiation
Sufficient energy to ionise matter (i.e. enough to cause chemical changes by breaking chemical bond)
Can break chemicals into individual ions
Non-ionising Radiation
Found at the long wave-length end of the spectrum and may have enough energy to excite molecules and atoms causing them to vibrate
Can’t break chemicals down, can excite them and make the move more (produce heat)
Ultraviolet (UV) Radiation
Invisible radiation produced naturally by the sun (solar radiation) and artificially in industry via arcs (e.g. welding) operating at high temperatures
Sources:
- sunlight
- electrical arc welding
- fluorescent lamps
- germicidal lamps
UVR - Electrical Arc Welding
Workplace epidemiology indicates that welders are at increased risk of ocular (eye) melanoma; less sure of arc welding UVR linkage to skin cancer
Infra-red Radiation
Transfer heat energy
Can damage cornea, iris, retina and lens of the eye
Laser Radiation
Light amplification by the stimulated emission of radiation
Concentrated beam of non-ionising radiation
Hazardous due to concentrated intensity
Radio-frequency Radiation
Ranges from ultra high frequency >300 GHz, to extremely low frequency 30-300Hz
Effects depend upon frequency but can include heating of the body, interference with normal functioning of body symptoms, etc.
Alpha Particles
Rapidly lose energy in matter and can be stopped by a sheet of thick paper
If inhaled (radon gas) or ingested it can cause severe tissue damage and cancer
A particle consisting of 2 protons and 2 neutrons
The loss produces a new element with a lower atomic number and mass
Beta Particles
Sufficient intensity of beta-radiation can cause burns, rather like sunburns
Can be stopped by 1-3mm aluminium
Occurs when the particle loses an electron from the nucleus, with too many neutrons, of the radioactive atom
Gamma Rays
A photon emitted by the nucleus of some radionuclides following radioactive decay
Can penetrate further
Thick concrete needed
X-Rays
Are high energy photons produced by the interaction of charged particles with matter
Produced when electrons strike a target or when electrons are rearranged within an atom
Stopped with a few mm of lead
Units for Measuring Radiation
Activity (Becquerel): Radiation is measured in decays (disintegrations) per second - corresponds to the number of nuclei losing energy each second
Absorbed Dose (Gray): A measurement of energy imparted to matter by ionising radiation per unit mass of material
Dose Equivalent (Sievert): Equal absorbed doses may not always give rise to equal risks of any biological effect
Dose Equivalent = Absorbed Dose x Modifying Factor
Radiological Protection
Time: Limiting or minimising amount of time people are exposed to radiation
Distance: radiation intensity decreases sharply with distances, according to inverse square law
Containment: Radioactive materials may be used in ‘sealed sources’ to prevent them spreading
Shielding: Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminium shielding
Lighting (quality/quantity)
Quantity: amount of illumination of the task. Measured by Lux, and must be sufficient for the worker to undertake the task
Quality: the suitability of the illumination
Good Lighting
Being able to see well saves energy, decreases risk of accidents, improving working conditions, increased productivity and decreased wastage due to errors, improves housekeeping and control
