. Biographies of distinguished scientific men. Scientists; genealogy. REFRACTIVE POWER. 141 in the 10th book of the Mecanique Celeste, and founded on the corpuscular hypothesis, the formulas would be dif- ferent for opaque and for transparent bodies. It is on A set of waves propagnted circularly from any source, when they get to a considerable distance, may be regarded as proceeding in par- allel planes. In all cases, the portions of circles or spheres which are their true form have a common tangent which marks what is called the "front" of the wave. But whenever waves encounter any
. Biographies of distinguished scientific men. Scientists; genealogy. REFRACTIVE POWER. 141 in the 10th book of the Mecanique Celeste, and founded on the corpuscular hypothesis, the formulas would be dif- ferent for opaque and for transparent bodies. It is on A set of waves propagnted circularly from any source, when they get to a considerable distance, may be regarded as proceeding in par- allel planes. In all cases, the portions of circles or spheres which are their true form have a common tangent which marks what is called the "front" of the wave. But whenever waves encounter any kind of obstacle, or enter any neio medium, then, from and round each point of such encounter, a new set of spherical waves begins to spread. In denser media these new waves spread more sloioly than in rarer, but when the obstacle is still surrounded by the same medium, then the velocity is unaltered. On these principles the ordinary laws of reflexion and refraction are proved on the theory of waves. In reflexion, if parallel waves u u! follow at equal intervals A, u im-. pinging on the sui'face at o, will cause a new circular wave to spread backwards from that point as a centre; when the next wave u' im- pinges at o', it will do the same, and so on in succession. But when the wave from o' has spread to a radius =X, that from o will have spread to a radius =2A, and so on. Hence to these contemporaneous circular waves drawing a common tangent r v' t this Avill be the front of the reflected waves, and the radii to the points of contact o «, of v', will give the inclination of the reflected rnys, which is easily seen to be equal to that of the incident, since oi v' =o' u—?i, and o v=^2ol v, whence 0 oi=oi t, and the triangles upon these equal bases being right-angled, the angle v t o=u o o/, or the angle of incidence, is equal to that of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - color
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