Sentence Examples


  • The instrument has a focal length of 54 ft.
  • But the eye is tolerant of small changes in the focal adjustment which sensibly affect the scale-value.
  • The amount of separation is very small, and depends on the thickness of the glass, the index of refraction and the focal length of the telescope.
  • They are placed at a distance apart less than the focal length of a, so that the wires of the micrometer, which must be distinctly seen, are beyond b.
  • An important property is: the difference of the focal distances of any point on the curve equals the transverse axis.