Sentence Examples


  • The amount of want of illumination in each portion of the penumbra is roughly indicated by the shading.
  • If we suppose the number of sources to increase indefinitely, so as finally to give the appearance of a luminous surface as the source of light, it is obvious that the degrees of darkness at different portions of the penumbra will also increase indefinitely; i.e.
  • There will be a gradual increase of brightness in the penumbra from total darkness at the edge next the geometrical shadow to full illumination at the outer edge.
  • But if we place a body at a distance of a foot or two only from the arc, the shadow cast will have as much of penumbra as if the sun had been the source.
  • The breadth of the penumbra when the source and screen are nearly equidistant from the opaque body is equal to the diameter of the luminous source.

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