| X-ray, pa | An X-ray picture in which the beams pass from back-to-front (posteroanterior). By contrast an ap (anteroposterior) film is one in which the rays pass through the body from front-to-back. (12 Dec 1998) |
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| X-ray therapy | Radiation therapy using X-rays; sometimes used ironically to refer to excessive use of diagnostic radiation. (05 Mar 2000) |
| slow ray | <microscopy> The slower of the two rays created by a crystal or fibre and the one that travels the path of higher refractive index. (05 Aug 1998) |
| spectrometry, X-ray emission | Identification and measurement of concentration of elements based on the fact that X-rays emitted by an excited element have a wavelength characteristic of that element and an intensity related to its concentration. It includes fluorescence, or secondary-emission, X-ray spectrometry, in which the specimen is irradiated by X-rays. Primary-emission x-ray spectrometry, in which the specimen is bombarded by electrons, is a specific type of X-ray emission spectrometry known as electron probe microanalysis. (12 Dec 1998) |
| densitometry, X-ray | Measurement of the degree of darkening of X-ray film by means of a photocell which measures light transmission through the film. (12 Dec 1998) |
| incident ray | The ray that strikes the surface before reflection. (05 Mar 2000) |
| infrared ray | See: infrared. (05 Mar 2000) |
| fast ray | <microscopy> The fast ray or fast component for a crystal or fibre corresponds to the lower refractive index. (05 Aug 1998) |
| lateral X-ray | An X-ray picture taken from the side. (12 Dec 1998) |