Dictionary - U

  • ultrasound: A branch of physics dealing with high frequency sound waves. Frequencies of various gigahertz can be produced by converting alternating electric currents into mechanical oscillations.
  • ultraviolet: electromagnetic radiation whose wavelengths range from 400 nm to 15 nm. It can be artificially produced in arc lamps; the one of natural origin comes from the sun.
  • astronomical unit: Unit of length used in astronomy, equivalent to the average radius of Earth's orbit, or about 150 million km.
  • uniform: That has only one form; which has the same shape; equal, identical; very similar; according. Monotonous, invariable; constant, regular.