Xrayspropagate

Xrayspropagate refers to the propagation of X-rays through space and matter, describing how this form of electromagnetic radiation travels, interacts, and is transformed along its path. In vacuum, X-rays move at the speed of light and follow straight-line trajectories, defined by Maxwell’s equations, with wavelengths roughly between 0.01 and 10 nanometers and photon energies from about 100 eV to 100 keV.

In materials, X-ray propagation is governed by absorption and scattering. The observed intensity decays with distance according to the Beer-Lambert law, I = I0 e^{-μx}, where μ is the linear attenuation coefficient that depends on photon energy and the material’s composition. The dominant interaction processes are photoelectric absorption, Compton scattering, and, at higher energies, pair production. These interactions enable imaging techniques such as radiography and computed tomography, while heavy elements increase attenuation, improving contrast in many applications.

The optical properties of X-rays in matter are unusual: their refractive index is very close to unity and slightly less than one, commonly written as n = 1 − δ + iβ with small δ and β. Refraction is weak, but X-rays can undergo total external reflection at small grazing angles, a principle exploited by specialized X-ray mirrors and optics to focus and steer X-ray beams.

Astronomically, X-ray propagation is affected by interstellar and intergalactic media, where gas, dust, and cosmic expansion influence attenuation and redshift the observed photons. Scattering by dust and absorption by heavy elements shape X-ray spectra from astronomical sources, informing studies of high-energy processes and the structure of the universe.