Light traveling through a transparent medium can be explained by assuming that high energy photons are larger than low energy photons. The delay of blue light relative to red light can be explained this way, and so can the greater diffraction of blue light than red light through a prism.
However, when dealing with opaque media, high energy photons like x-rays and gamma.rays are used for translucence. Visible light barely manages to make its way through a finger or a hand,even if very bright. The kind of sharpness of image that can be achieved with x-rays is impossible to achieve with visible light, and the reason for this is fairly uncontroversial.
When it comes to x-rays, the light is treated as particles by pretty much all schools of thought. The explanation for why x-ray pictures can give such defined images of bones and objects inside our bodies is that they smash their way through matter with their enormous momentum. They are like bullets whizzing through our soft flesh and bones. The softer, most translucent part of us, such as muscle tissues, let through the most x-rays. Harder, less translucent part of us, like bones and nails, let through less x-rays.
There is very little bouncing about as an x-ray photon makes its way through a body. It is either stopped dead in its track, or it is let through. That's why the images taken with x-rays end up as sharp and defined as they do.
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