. The Ontario high school physics. Fig. 391.—Plane waves made spherical bya converging lens. In Fig. 391 plane waves (parallelrays) fall on the lens. Now theirvelocity in. glass is only | that inair, and that part of the waveswhich passes through the central part of the convex lens will be delayed behind that which traversesthe lens near its edge, and the result is, tlie waves are concave onemerging from the lens. They continue moving onward, continuallycontracting, until they pass through F, the principal focus, andthen they enlarge. In Fig. 392 spherical waves spread out from P. On traversin
. The Ontario high school physics. Fig. 391.—Plane waves made spherical bya converging lens. In Fig. 391 plane waves (parallelrays) fall on the lens. Now theirvelocity in. glass is only | that inair, and that part of the waveswhich passes through the central part of the convex lens will be delayed behind that which traversesthe lens near its edge, and the result is, tlie waves are concave onemerging from the lens. They continue moving onward, continuallycontracting, until they pass through F, the principal focus, andthen they enlarge. In Fig. 392 spherical waves spread out from P. On traversingthe central portions they are held back by the thicker part of the. ii3i*-«i«ii Fig. 392.—Waves expanding- from P are changed by the lens intocontracting spherical waves. lens, and on emerging they ai-e concave, but they do not convergeas rapidly as in the first case. In Fig. 393 is shown the effect ofa concave lens. The outer portionsof the lens being thicker than thecentral, retard the waves most, withthe result that the convexity of thewaves is increased, so that theymove off having P as their centre. Fig. going out from p are These results are further illus- niade more curved by the lens, and ..i- i-i- i ^ ,.ci appear to have P as their centre. trated m a Stllkmg and beautltul manner by using an air lens inan atmosphere of water. Such a lens can be constructed withoutdifficulty by cementing two watch-glasses into a turned wooden
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
