• Question: why use x rays if there are lots of other rays to use?

    Asked by angelica to Andrew on 16 Nov 2011.
    • Photo: Andrew Cairns

      Andrew Cairns answered on 16 Nov 2011:

      The answer to this question depends on how waves (essentially packets of energy) interacts with matter (mass).

      For a successful experiment where the rays diffract (change direction) in a meaningful way, the wavelength of the wave (the distance between next-door peaks) must be similar to the distance between atoms. Other rays have longer (for example, microwaves) or shorter (for example, gamma rays) and therefore do not diffract in a meaningful way.

      That is not to say other rays are not useful! Every part of the electromagnetic spectrum can be used to excite an atom or a molecule in a different way. For example, Infrared radiation causes bonds to vibrate, whilst ultraviolet can make molecules rotate. This is all a type of analytical chemistry called ‘spectroscopy’ which is separate from diffraction.

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