Diagnostic medical sonography (DMS) uses. high frequency sound waves to produce images. (sonograms) of structures such as the liver, heart. or unborn baby that can be visualized on a video. monitor. Sonography is often referred to as. âultrasoundâ or âultrasonographyâ. Sonography. can be used to examine many parts of the body. including organs in the abdomen, the breast, the. uterus and ovaries, the prostate gland, the heart. and blood vessels.
principle of superposition - the displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point; the principle of superposition is the basis of the wave theory of light. Huygens' principle of superposition.
The principle of uniformitarianism - processes operating in the past were constrained by the same laws of physics as operate today. Note that these are principles. In no way are they meant to imply there are no exceptions. For example, the principle of superposition is based, fundamentally, on gravity. In order for a layer of material to be deposited, something has to be beneath it to support it. It can't float in mid-air, particularly if the material involved is sand, mud, or molten rock. The principle of superposition therefore has a clear implication for the relative age of a vertical succession of strata. There are situations where it potentially fails -- for example, in cave deposits.