Wave length, Compton

I will only state the form of the result at large r (that is, r large compared to the Compton wave length of either particle) and... 

The relation between the mass (or momentum) of the light quantum and the wave length of the radiation is confirmed experimentally by the observation of the Compton effect. In this effect, the change of the wave length of X-radiation when the latter is scattered by an electron, the experimental result can be calculated simply by treating not only the electron but also the quantum of radiation as material particles colliding with one another. 

As well as the coherent scattering, which has the same wavelength as the incident waves, an atom scatters waves of reduced wave-length. The intensity of these waves is not included in the formulae (I) and (2). For X-rays falling on a hydrogen atom, the total intensity scattered inelastically, due both to Raman effect and Compton effect, is given by the formula... 

Compton (1922) investigated the scattering of X-rays by a block of paraffin, and found that the radiation scattered at an angle of less than 90° possesses a greater wave-length than the primary radiation, so that the v of the scattered wave, contrary to the prediction of the classical theory, is smaller than the v of the... 

Delta is of the order of 10 and is typically of the order of a few milliradians. As long as the beam is incident below this critical angle, it is totally reflected and only an evanescent wave penetrates the substrate. This has two very important consequences. First, the penetration depth is of the order of 20 A and thus one can signiflcantly discriminate in favor of a surface-contained material. Compton and elastic scattering are also minimized. In addition, the reflection enhances the local intensity by as much as a factor of 4 as well as the effective path length. All of these factors combined enhance the surface sensitivty of the technique and when combined with solid-state fluorescence detection, submonolayer amounts of material can be detected. ... 

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