. A text book of physics, for the use of students of science and engineering . Double Piano- Concavo-Convex Convex Convex DoubleConcave Piano-Concave Convexo-Concave Converging Lenses Diverging Lenses Fig. 537.—Classification of lenses. Refraction at single spherical surface.—In order to obtain the lensformula, the production of an image by a single refracting surfacewill be treated first, and the result then applied to an actual lens,which has, of course, two refracting surfaces. _ In Fig. 538 let A, in either diagram, be a point source of lightsif uated on the principal axis. A ray such as A
. A text book of physics, for the use of students of science and engineering . Double Piano- Concavo-Convex Convex Convex DoubleConcave Piano-Concave Convexo-Concave Converging Lenses Diverging Lenses Fig. 537.—Classification of lenses. Refraction at single spherical surface.—In order to obtain the lensformula, the production of an image by a single refracting surfacewill be treated first, and the result then applied to an actual lens,which has, of course, two refracting surfaces. _ In Fig. 538 let A, in either diagram, be a point source of lightsif uated on the principal axis. A ray such as AB will, on enteringthe glass, be refracted along BD. In Fig. 538 (a) we have sin ABE _ sin i sinCBD sin r ~ ^and in Fig. 538 (b) we have sin ABC sin i sin EBD sin / ,/*? JLVI SPHERICAL REFRACTING SURFACES 589 Draw BP perpendicular to the axis ; then from either diagram,since all the rays are much nearer the axis than is shown in:.he diagrams, 0 = BPA u BP BP i + r = —v Y and .BP BP u rx BP BP v FIG. 538.—Spherical refracting surface. It must be remembered that in Fig. 538 (a), rx is essentiallylegative, in accordance with the convention of signs. Again, wheni and r are small, we may, without sensible error, write sin % _ % _sin r r or Hence, BP u or BP H1 u I1 BP v -1 i = This gives the relation between u and v for a single spherical refract-ing surface. The equation is more complicated than for a sphericalmirror, and involves the refractive index of the medium, which itobviously must do. ; Expt. 127.—Refraction at a curved surface. Place a pin A (Fig. 5* (2)upright inside a glass crystallising basin containing water, fixing itmeans of soft wax. Let the basin rest upon a sheet of drawing paj 590 LIGHT CHAP. Fix two other pins at B and C, in line with the image I as seen by the fix other pairs of pins at DE, FG, etc. Mark the outline of the
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
