Biophotonics_Concepts_to_Applications

ranges listed in the literature often vary slightly from those shown in Table1.5,
which are based on the designations given in Document ISO- 21348 of the
International Standards Organization. Note that the UV spectral region is parti-
tioned into three bands that are classified as UV-C, UV-B, and UV-A. The reason
for these designations is that the UV light energy is stronger than visible light and
its effects are different in each band. Natural sunlight at the surface of the earth
contains mainly UV-A and some UV-B lightwaves. UV-A light is slightly more
energetic than visible blue light. Many plants use UV-A for healthy growth and, in
moderate doses, UV-A light is responsible for skin tanning. Health concerns for
exposure to UV light are mostly in the UV-B range. The most effective biological
wavelength for producing skin burns is 297 nm. The adverse biological effects
increase logarithmically with decreasing wavelength in the UV range, with 330 nm
being only 0.1 % as effective as 297 nm. Thus it is quite important to control
human exposure to UV-B. UV-C light has the highest energy. Although the sun
emits UV-C wavelengths, the upper atmospherefilters out this band, so there is no
exposure to UV-C from sunlight on earth. However, because UV-C light is used for

10 -2

108 1010 1012 1014 1016 1018

103

Frequency

(Hz)

Photon energy (eV)

Wavelength

(m)

HF/UHF/VHF Radio Microwaves X rays

Infrared 1.7 μm to 1 mm

Biophotonics

190 nm to 10.6 μm

(~6.5 to 0.23 eV)

Ultraviolet

Visible light

400-700 nm

10 -4 10 -6 10 -8

10 -5 10 -3 0.1 10

1

Fig. 1.5 Location of the biophotonics discipline in the electromagnetic spectrum

Table 1.5 Wavelength and photon energy ranges for various optical spectrum bands (Spectral
band ranges are based onDocument ISO-21348 of the International Standards Organization)

Band designation Wavelength range (nm) Photon energy range (eV)

UV-C 100 – 280 12.4–4.43

UV-B 280 – 315 4.43–3.94

UV-A 315 – 400 3.94–3.10

Visible 400 – 700 3.10–1.63

Near infrared (IR-A) 700 – 1400 1.63–0.89

Mid infrared (IR-B) 1400 – 3000 0.89–0.41

10 1 Overview of Biophotonics