From New Latin focālis; synchronically analyzable as focus + -al.
Focal 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.
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.
A rotation of this amount should therefore be easily visible, but the limits of resolving power are being approached; and the conclusion is independent of the focal length of the mirror, and of the employment of a telescope, provided of course that the reflected image is seen in focus, and that the full width of the mirror is utilized.