UV-Microwaves Flashcards
(31 cards)
What is the UV (A, B and C) dose limit to the eye and skin?
Eeff = 30 Jm-2
for all UV (180-400 nm), time averaged over 8 hour day
UVA: 10000
What wavelength is UVA?
400 - 315 nm.
What wavelength is UVB?
315 - 280 nm.
What wavelength is UVC?
280 - 100 nm.
What are the UV effects on the eye?
- Inflammation
- Conjuctivitis
- Cataract formation
What is MED?
Minimal Erythemal Dose:
Lowest dose of UVR that will produce a barely detectable erythema.
It depends on skin type.
I-II: <300 Jm-2
III: 600 Jm-2
IV: 800 Jm-2
V-VI: 1000 Jm-2
What do the severity of UV effects depend on?
- UV level
- Duration and frequency of exposure
- Individual sensitivity
What is UV?
The portion of the EM spectrum from visible to ~100 nm, and is divided up into 3 bands (UVA, UVB, UVC).
Which UV band is the least energetic?
UVA
Which UV band is responsible for sun tan effects?
UVB
What are some natural protection mechanisms from UV?
Skin darkening (increase in pigment) and skin thickening (increase in cell proliferation).
What are the UV effects on skin?
Erythema, basal cell carcinoma, squamous cell carcinoma and malignant melanoma, ageing, loss of elasticity, dryness, freckles/moles.
What are beneficial systemic effects of UV?
- Vitamin D production
- Seasonal Affective Disorder
- Medical treatment/therapy
What are the negative systemic effects of UV?
Compromised immune system (UV radiation is an immuno-suppressor).
What is MPE for UV?
Maximum Permissible Exposure:
Highest power of a source that is considered safe.
What is the MPE and Spectral Effectiveness for UV with a wavelength of 270 nm?
MPE = 30 Jm-2
SE = 1.0
How is the MPE time calculated?
tmax = 30/Eeff
What are the UVA limits when unprotected?
Total irradiance < 10 Wm-2 (for exposure time >1000s
Total irradiance < 10^4 Jm-2 (for exposure time <1000s)
Averaged over 8 hr period
How are patients kept safe from UV exposure?
Glasses or goggles
Protection from electrical hazards
Doors openable from within cabinet
Non-skid flooring
What are the principles of UV protection?
Design
Maintenance
Signs and labels
Limit access
Training
QA
Local rules
Reduce time
Shielding - clothes, drapes, eyewear
What is the wavelength range for microwaves and RF?
> 10^3 - 10^-2 m (3 kHz - 300 GHz)
What is a hazard due to microwaves and RF?
Heating
How is heating by microwaves and RF quantified?
SAR - Specific Absorption Rate
SAR prop to xE^2/rho
x - electrical conductivity of tissue
E - rms E field
rho - density of tissue
(Wkg-1)
What is the SAR temperature rule for microwaves?
SAR=4 Wkg-1 raises the body temperature by 1 degree
