. The Ontario high school physics. lens,and if y is its focal length, OC = y approximately. Also puttingOB = A, the least distance of distinct vision, we have AMagnification = —r* For example, if focal length = 1 cm. and A = 26 cm., thenmagnification = 25 -r 1 = 25. It might be noted that since P, the poiver of a lens, is inverselyproportional to its focal length (§ 382) Magnification = A x P. The smaller the focal length the greater is the power and also themagnification. The greatest magnification, however, which can beobtained is about 100. 416. The Compound Microscope. For higher magnifica
. The Ontario high school physics. lens,and if y is its focal length, OC = y approximately. Also puttingOB = A, the least distance of distinct vision, we have AMagnification = —r* For example, if focal length = 1 cm. and A = 26 cm., thenmagnification = 25 -r 1 = 25. It might be noted that since P, the poiver of a lens, is inverselyproportional to its focal length (§ 382) Magnification = A x P. The smaller the focal length the greater is the power and also themagnification. The greatest magnification, however, which can beobtained is about 100. 416. The Compound Microscope. For higher magnificationswe must use a combination of convex lenses known as a compoundmicroscope. In its simplest form it consists of two lenses, theobjective and the eyepiece, the action of which is illustrated inFig. 433. THE ASTRONOMICAL TELESCOPE 3G3 The object PQ is placedat A, before the objective 0 and justbeyond its principal focus. Thus a real enlarged inverted imagePQ is produced at B, and the eyepiece E is so placed that FQ is <Zi^. Fig. 433.—Diagram illustrating the compound microscope. just within its focal length. The eyepiece E then acts as a simplemicroscope magnifying !(/. It forms an enlarged virtual imagepq at the distance of distinct vision from the eye. This distanceis approximately the length L of the microscope tube. We see, then, that the objective and the eyepiece both magnifythe object, and the total magnification is obtained by compowiding(, nmltiplying) these two magnifications. The magnification produced by the objective = ?19^, which = — (see 3 389). Now AO = F, the focal length of objective, approximately,and BO = L, the length of the nucroscope tube, approximately. Mence —i- = - , approxmiately. Also, if / = focal length of eyepiece (in cm.), 25Magnification by eyepiece = -_ (§ 415) and total magnification = — x - = F f Ff 417. The Astronomical Telescope. The arrangement of thelenses in the astronomical telescope is the same in principle as inthe
Size: 2119px × 1179px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
