Questions about light absorption

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SUMMARY

This discussion focuses on the mechanisms of light absorption, particularly in the extreme ultraviolet (EUV) and hard X-ray regions. It establishes that materials absorb EUV light due to the energy of photons matching atomic energy level differences, leading to atomic excitation and subsequent energy release. In contrast, hard X-rays can penetrate materials because their high energy can ionize atoms, although they do not pass through all substances. The importance of x-ray absorption spectroscopy is highlighted as a key analytical tool in this context.

PREREQUISITES
  • Understanding of atomic energy levels and photon interactions
  • Familiarity with the concepts of ionization and excitation in atoms
  • Knowledge of x-ray absorption spectroscopy techniques
  • Basic principles of black body radiation
NEXT STEPS
  • Research the principles of x-ray absorption spectroscopy and its applications
  • Study the differences in light absorption between atomic gases and solids
  • Explore the role of phonons in material absorption processes
  • Investigate the effects of photon energy on atomic excitation and ionization
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Physicists, materials scientists, and anyone interested in the interactions between light and matter, particularly in the context of spectroscopy and material analysis.

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It is to do with how absorption happens.

Let's see if I can give you a simple model:

A photon encounters an atom, it is absorbed if the energy of the photon matches closely enough with the difference in energy between two atomic energy levels. The atom becomes excited for a while, then releases the energy in a series of lower energy jumps or mechanically by jostling adjacent atoms ... so the material heats up.

The higher the energy of the photon, the bigger the energy hit, and for very high energy (eg x-rays or gamma rays) the energy is enough to ionize the atom. Thus even x-rays do not go through everything. In fact, x-ray absorption spectroscopy is an important tool.

For a wider discussion see:
https://www.physicsforums.com/showthread.php?t=317716
 
There is a difference between absorption by atomic gasses, versus absorption by a solid. Please read the FAQ subforum in the General Physics forum, especially the discussion on "phonons".

Zz.
 

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