Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

Solution
NONIONIZING RADIATION SAFETY 723
The energy of a 400-nm UV photon is calculated with Eq. (2.77):
E = h c
λ = 6.6262 × 10−34 8 m
3 × 10
J · s ×
s
400 × 10 −9 m = 4.97 × 10−19 J
= 4.970 × 10−19 J
1.6 × 10−19 = 3.1eV,
J
eV
and the frequency of this photon is calculated from Eqs. (2.76) and (2.77):
UV LIGHT
Sources
E = hf = h c
λ ,
f = c
λ = 3 × 108 m/s
400 × 10 −9 m = 7.5 × 1014 s −1 = 750 THz (terahertz).
UV radiation is defined by the WHO as light with wavelengths between 100 nm
and 400 nm. The UV spectrum is divided into three regions: UVA, 320–400 nm;
UVB, 280–320 nm; and UVC, 100–280 nm. Other common names for the different
portions of the UV spectrum include actinic UV, UVA and UVB; far UV, UVC; and
near UV, UVA. UVC is not transmitted through the atmosphere; it therefore is often
referred to as vacuum UV.
The sun is the largest source of UV radiation; the sunlight that reaches the earth’s
surface consists mainly of UVA radiation, with a smaller component of UVB. All of
the UVC is filtered by the ozone layer, and thus no UVC reaches the earth’s surface.
Man-made sources of UV radiation include:
black light lamps
carbon arcs
dental polymerizing instruments
fluorescence equipment
germicidal lamps
hydrogen lamps
metal halide lamps
mercury lamps
plasma torches
printing ink polymerization
tanning equipment
welding arcs