The fronts of these secondary waves all lie on a surface, which becomes the new surface of the primary wave.
The operative part, or parts, of the curve are of course those which represent the unobstructed portions of the primary wave.
The conception of the lamina leads immediately to two schemes, according to which a primary wave may be supposed to be broken up.
For a point Q outside the shadow the integration extends over more than half the primary wave.
But a little consideration will prove that in that case the series of secondary waves could not reconstitute the primary wave.
|primary wave |
A type of seismic body wave in which rock particles vibrate parallel to the direction of wave travel. Primary waves are alternatingly compressional and extensional, and cause the rocks they pass through to change in volume. These waves are the fastest traveling seismic waves and can travel through solids, liquids, and gases. Also called P wave. See Note at earthquake.