Radiation particle nature

The exposure to ionizing radiation from natural sources is continuous and unavoidable. For most individuals, this exposure exceeds that from all human-made sources combined (UNSCEAR 2000a). The two main contributors to natural radiation exposures are high-energy cosmic ray particles incident on the earth s atmosphere and radioactive nuclides that originate in the earth s crust and are present everywhere in the environment, including the human body itself. 

This, plus the quantization of the normal modes of vibration of the electromagnetic radiation field (just demonstrated), form, together, the quantum-mechanical basis for the wave-particle duality A wave can become a particle, and vice versa, but you can never make a simultaneous experiment to test both the wave and the particle nature of the same system. 

Cancer. There has been interest in the potential carcinogenicity of uranium, which emits alpha-particle radiation, although natural, depleted, or enriched uranium or uranium compounds have not been evaluated in rodent cancer bioassays by any route by the NTP (BEIR 1980, 1988, 1990 Hahn 1989 Otake and Schull 1984 Sanders 1986 UNSCEAR 1982, 1986, 1988). However, there is no unequivocal evidence that inhalation, oral, or dermal exposure induces cancers in humans because it is difficult to isolate the... 

Photoelectric effect The photoelectric effect demonstrated the particle nature of electromagnetic radiation (formerly described only as waves). 

This mean value e is independent of the nature of the radiating system (oscillator), as follows at once from the method of calculating it it must hold in exactly the same form for a system of atoms or other radiating particles. 

A radioactive isotope radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay and emits gamma ray(s), subatomic particles, or both. Radionuclides occur naturally, but can also be artificially produced. 

The Compton effect, discovered in 1922, was treated earlier in this chapter. This nonelastic scattering of X-rays established the particle nature of radiation. In an extension of this work, a young Indian physicist, Chrandrasekhara Venkata ( C. V. ) Raman (1888-1970), working in Calcutta, investigated the scattering of visible light. 

Spectra collected by these fom methods of an oxidized layer on 50-70-p,m galena particles (natural PbS, n 4) using the same number of scans (100) and resolution (4 cm ) and a Perkin-Ehner 1760X FTIR spectrometer equipped with a mercury-cadmium-teUmium detector are shown in Fig. 2.51. Because of strong backscattering by the PbS particles and, as a result, a small penetration depth of radiation, the transmission spectrum obtained from the powder squeezed between two plane-parallel KBr plates represents mainly the component /q that has passed by the particles (Fig. 1.22) and, hence, bears no information on the sample absorption. The DRIFTS and DTIFTS spectra of the PbS powder and the transmission spectrum of a mixture of PbS and KBr spectra are more informative. The distinct absorption bands of surface oxidation products at 1440, 1400, and 1200-1100 cm are assigned to lead carbonate, hydroxide, and sulfoxide [109],... 

One very powerful tool for determining the size, shape, and orientation of colloidal particles in a liquid continuum is through their interaction with X-radiation. The nature of this interaction varies considerably with the colloidal system, and it can often be used to elucidate the structure of the latter when combined with the results of other experimental measurements. X-ray results alone rarely lead to unambiguous conclusions in these kinds of systems. 

This dual wave/particle nature is the basis of the quantum theory of electromagnetic radiation, which states that radiant energy can be absorbed or emitted only in discrete packets called quanta or photons. The energy E of each photon is given by... 

Although shown to have some serious flaws and long since abandoned, the Bohr model laid the groundwork for the more sophisticated theories of atomic structure that are accepted today and introduced the all-important concept that only specific energy states are allowed for an electron in an atom. Like electromagnetic radiation, electrons in atoms are now visualized as having a dual wave/particle nature. 

The Compton scattering was the first observation of the dual - wave and particle - nature of electromagnetic radiation. 

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