Operating Manual

2
Basic properties
of ionising radiation
19
In 1895 the physicist Wilhelm Conrad Röntgen discovered a new kind of radiation, which
he called X-rays. The rays were generated when high energy electrons were suddenly
stopped by striking a metal target inside a vacuum tube – the X-ray tube.
It was subsequently shown that X-rays are an electromagnetic radiation, just like light,
heat and radiowaves.
2.1 Wavelengths of electromagnetic radiation
The wavelength lambda (λ) of electromagnetic radiation is expressed in m, cm, mm,
micrometer (μm), nanometer (nm) and Ångstrom (1 Å = 0.1 nm).
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Electromagnetic radiation Wavelength λ m Type
10 km 10
4
1 km 10
3
100 m 10
2
10 m 10
1
1 m 1
10 cm 10
-1
1 cm 10
-2
1 mm 10
-3
100 μm 10
-4
10 μm 10
-5
1 μm 10
-6
100 nm 10
-7
10 nm 10
-8
1 nm 10
-9
0.1 nm 10
-10
0.01 nm 10
-11
1 pm 10
-12
0.1 pm 10
-13
0.01 pm 10
-14
X-ray energy
100 eV
1 keV
10 keV
100 keV
1 MeV
10 MeV
100 MeV
Visible light and Ultraviolet (UV)
X-rays and Gamma-rays
(Radiography)
Heat-rays, Infra-red rays,
microwaves
Table 1-2. Overview of wavelength, energy and type of electromagnetic radiation