. A text book of physics, for the use of students of science and engineering . IPf B Fig. 488.—Shadow when source of light is not a point. if a screen be placed at A, there will be a small region of denseshadow surrounded by a large region of half shadow, but if the. Fig. 489.—Shadow with source of considerable size. screen be placed at B, there will be no complete shadow, merely alarge, diffuse half shadow. 540 LIGHT chap. Expt. 112.—Shadows. Cut a hole of 10 cm. diameter in a sheet of card-board, and cover the hole with oiled paper. Behind this place the brightestsource of illumination avail
. A text book of physics, for the use of students of science and engineering . IPf B Fig. 488.—Shadow when source of light is not a point. if a screen be placed at A, there will be a small region of denseshadow surrounded by a large region of half shadow, but if the. Fig. 489.—Shadow with source of considerable size. screen be placed at B, there will be no complete shadow, merely alarge, diffuse half shadow. 540 LIGHT chap. Expt. 112.—Shadows. Cut a hole of 10 cm. diameter in a sheet of card-board, and cover the hole with oiled paper. Behind this place the brightestsource of illumination available. In front of the sheet place a circle ofcardboard of 20 cm. diameter ; observe the shadows produced on a neigh-bouring wall. Replace the 20 cm. circle by one of 5 cm. diameter andnote that the shadow as at A or at B may be obtained (Fig. 489), accordingto whether the screen is at A or B. Eclipses.—An example of shadows on an astronomical scaleoccurs in the case of eclipses. It sometimes happens at new moonthat the shadow of the moon falls upon the earth, in which casethe sun is wholly or partially obscured by the moon, and we get aneclipse of the sun. In Fig. 490, some locality A, on the earth E,falls within the shadow of the moon mx, and there is
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
