. The principles of physics. sposition of a pencil of rays emanatingfrom any point ( A) after reflection from a convex an image of an object placed in front of a convexmirror. 302. Illustrative experiments. Experiment 3. —Hold some object, a rose, as a6 (Fig. 249), a fewfeet in front of a concave mirror. Looking in the direction of the axis of the mirror you see asmall inverted image,AB, of the object, be-tween the center of cur-vature, C, of the mirrorand its principal focus,F. Evidently if AB rep-resent an object placedbetween the principalfocus and the center ofcur
. The principles of physics. sposition of a pencil of rays emanatingfrom any point ( A) after reflection from a convex an image of an object placed in front of a convexmirror. 302. Illustrative experiments. Experiment 3. —Hold some object, a rose, as a6 (Fig. 249), a fewfeet in front of a concave mirror. Looking in the direction of the axis of the mirror you see asmall inverted image,AB, of the object, be-tween the center of cur-vature, C, of the mirrorand its principal focus,F. Evidently if AB rep-resent an object placedbetween the principalfocus and the center ofcurvature, then a 6 willrepresent the image ofthe .#. —Place a candle in an otherwise dark room 20 feetfrom the mirror, catch the focused light-waves upon a paper screen, andshow that the focus Is about half-way between the vertex and the centerof curvature of the mirror. Experiment B. — Advance the distant candle flame toward the mirror,moving it up and down. (1) Show that the focus advances to meet the. Fig. 249. 344 ETHBB, DYNAMICS. flame, and that when the flame is raised the foeUs is depressed, and theconverse. (2) Show that when the flame is at the center of curvature,the focus is also there. (3) Show that when the flame is between thecenter of curvature and the principal focus, the focus of the flame isfarther away than the center of curvature. (4) Show that when theflame is at the principal focus, the reflected rays are parallel, or the focusis at an infinite distance. (5^ Show that when the flame is still nearer,the reflected rays diverge and appear to come from a point behind themirror. (6) Notice that in all cases except the last the images are realand inverted, and that in all cases where a real image is formed, theflame and the image may change places. Experiment 6. — Form a Ieal Image of the flame between yourself andthe mirror; view the image through a convex lens (§ .318); show thatthe image can be magnified by a convex lens, and thereby
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
