Generalities on X-rays
X-rays, as visible light or radiation \(\gamma\), are electromagnetic radiation (see diagram below). They are characterized by a sinusoidal electromagnetic field that propagates at the speed of light.
The principal characteristics of this radiation are:
its frequency \(\nu\) expressed in Hertz (\(\textrm{Hz}\)),
its wavelength \(\lambda\) expressed in metres (m) or more conveniently in angstroms (\(1 Å = 10^{-10} \textrm{ m}\)),
its energy E expressed in Joules (\(\textrm{J}\)) or more commonly in electron-volts (\(1 \textrm{ eV} = 1.6 \times\textrm{10}^{-19} \textrm{ J}\)),
its intensity \(I\) expressed in Watts per steradian (energy traversing the unit of solid angle per unit time)
Radiation energy is quantified and is transported as photons. This energy is written as:
\(E = \frac{hc}{\lambda} = h\nu\)
where \(h\) is the Planck constant (\(6.626 \times\textrm{10}^{-34}\textrm{J.s}\)) and \(c\) the speed of light (\(3.1 \times \textrm{10}^8 \textrm{ m.s}^{-1}\)).